Ruby CSV Standard Library

https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/
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### Setup for CSV Table Examples

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Sets up a string and a file path for use in CSV table examples.

```ruby
string = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
path = 't.csv'
File.write(path, string)
```

--------------------------------

### Setup for CSV Examples with Headers

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Sets up a string and a file path for use in CSV parsing examples with headers.

```ruby
string = "Name,Count\nfoo,0\nbar,1\nbaz,2\n"
path = 't.csv'
File.write(path, string)
```

--------------------------------

### Install Built-in Field Converters

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Installs built-in field converters like `:integer`, `:float`, or `:date`. Returns an array of installed converters.

```ruby
csv = CSV.new('')
csv.convert(:integer)
csv.convert(:float)
csv.convert(:date)
csv.converters # => [:integer, :float, :date]

```

--------------------------------

### Install Field Converter by Name with Block

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Installs a field converter by its name. If a block is provided, it will not be called, as the converter is already defined.

```ruby
csv = CSV.open(path)
csv.convert(:integer) {|field, field_info| fail 'Cannot happen' }
csv.read # => [["foo", 0], ["bar", 1], ["baz", 2]]

```

--------------------------------

### Define CSV String

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Example string input for parsing.

```ruby
string = "foo,0\nbar,1\nbaz,2\n"
```

--------------------------------

### Define input for skip_lines example

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Sets up the input string containing comments to be skipped.

```ruby
str = <<-EOT
# Comment
foo,0
bar,1
baz,2
```

--------------------------------

### Define and Install Custom Field Converter

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Defines and installs a custom field converter using a block. The block is called for each field and receives the field value and a `CSV::FieldInfo` object.

```ruby
string = "foo,0\nbar,1\nbaz,2\n"
path = 't.csv'
File.write(path, string)

csv = CSV.open(path)
csv.convert {|field, field_info| p [field, field_info]; field.upcase }
csv.read # => [["FOO", "0"], ["BAR", "1"], ["BAZ", "2"]]

```

```ruby
csv = CSV.open(path)
csv.convert {|field, field_info| field.to_sym }
csv.read # => [[:foo, :"0"], [:bar, :"1"], [:baz, :"2"]]

```

--------------------------------

### Raise ArgumentError Example

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Demonstrates an ArgumentError when trying to parse nil as CSV.

```ruby
# Raises ArgumentError (Cannot parse nil as CSV):
CSV.parse_line(nil)
```

--------------------------------

### CSV encoding options

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Example of specifying encoding options for CSV parsing.

```ruby
hash form:
  :invalid => nil      # raise error on invalid byte sequence (default)
  :invalid => :replace # replace invalid byte sequence
  :undef => :replace   # replace undefined conversion
  :replace => string   # replacement string ("?" or "\uFFFD" if not specified)
```

```ruby
encoding: 'UTF-32BE:UTF-8'
```

--------------------------------

### Get Lines to Skip - CSV::Parser

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser.html

Returns the number of initial lines to skip before starting CSV parsing. This is an internal method.

```ruby
def skip_lines
  @skip_lines
end
```

--------------------------------

### CSV Data Representation

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Example of a CSV string with row and column separators.

```text
"foo,0\nbar,1\nbaz,2\n"
```

--------------------------------

### Specify encoding for CSV.foreach

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Example of providing an encoding option to transcode data while reading.

```ruby
encoding: 'UTF-32BE:UTF-8'
```

--------------------------------

### Read lines

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser/UnoptimizedStringIO.html

Delegates the gets method to the underlying StringIO object.

```ruby
def gets(*args)
  @io.gets(*args)
end
```

--------------------------------

### Retrieve CSV rows by index

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Table.html

Examples demonstrating how to extract rows from a CSV::Table using integers, ranges, or a combination of both.

```ruby
source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
table = CSV.parse(source, headers: true)
table.values_at # => []
```

```ruby
values = table.values_at(0)
values # => [#<CSV::Row "Name":"foo" "Value":"0">]
```

```ruby
values = table.values_at(2, 0)
values # => [#<CSV::Row "Name":"baz" "Value":"2">, #<CSV::Row "Name":"foo" "Value":"0">]
```

```ruby
values = table.values_at(1..2)
values # => [#<CSV::Row "Name":"bar" "Value":"1">, #<CSV::Row "Name":"baz" "Value":"2">]
```

```ruby
values = table.values_at(0..1, 1..2, 0, 2)
pp values
```

--------------------------------

### CSV Instance Method: convert

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Installs or defines field converters for the CSV object. Can be used with or without a block.

```APIDOC
## convert

### Description
Installs or defines field converters for the CSV object. When called with a `converter_name`, it installs a built-in converter. When called with a block, it defines and installs a custom converter.

### Method
`convert(converter_name)` or `convert {|field, field_info| ... }`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
* **converter_name** (Symbol) - Optional - The name of a built-in field converter to install (e.g., `:integer`, `:float`, `:date`).
* **Block** - Optional - A block that takes `field` and `field_info` as arguments and returns the converted field value.

### Request Example
```ruby
# Install built-in converters
csv = CSV.new('')
csv.convert(:integer)
csv.convert(:float)

# Define a custom converter
csv.convert do |field, field_info|
  field.upcase
end
```

### Response
#### Success Response (200)
* **Array of Procs** - Returns an array of the currently installed field converters.

#### Response Example
```ruby
# Returns an array of Proc objects representing the converters.
```

### Error Handling
* Raises a parse-time exception if `converter_name` is not a recognized built-in converter.
```

--------------------------------

### Raise NoMethodError Example

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Demonstrates a NoMethodError when trying to call 'close' on a Symbol.

```ruby
# Raises NoMethodError (undefined method `close' for :foo:Symbol)
CSV.parse(:foo)
```

--------------------------------

### Field Converter with Field Info

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

A converter proc can accept a second argument, `field_info`, providing details like index, line number, and header. This example prints the arguments before stripping whitespace.

```ruby
strip_converter = proc do |field, field_info|
  p [field, field_info]
  field.strip
end
string = " foo , 0 \n bar , 1 \n baz , 2 \n"
array = CSV.parse(string, converters: strip_converter)
array # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
```

--------------------------------

### Retrieve CSV column data

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Table.html

Examples showing how to extract specific column data from a CSV::Table using header names.

```ruby
values = table.values_at('Name')
values # => [["foo"], ["bar"], ["baz"]]
values = table.values_at('Value', 'Name')
values # => [["0", "foo"], ["1", "bar"], ["2", "baz"]]
```

--------------------------------

### Start saving state in CSV::Parser::InputsScanner

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser/InputsScanner.html

Saves the current scanner position to the internal stack.

```ruby
def keep_start
  @keeps.push([@scanner.pos, nil])
end
```

--------------------------------

### GET /CSV::Table/get

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Table.html

Retrieves data from the table based on index, range, or header.

```APIDOC
## GET /CSV::Table/get

### Description
Returns data from the table without modifying it. Supports indexing by row number or column header.

### Parameters
#### Query Parameters
- **n** (Integer|Range|String) - Required - The index, range, or header name to retrieve data for.
```

--------------------------------

### CSV generation with multiple write converters

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Applies multiple `write_converters` in sequence. The example shows converting fields to uppercase and then to lowercase, resulting in the original case.

```ruby
upcase_converter = proc {|field| field.upcase }
downcase_converter = proc {|field| field.downcase }
write_converters = [upcase_converter, downcase_converter]
str = CSV.generate_line(['a', 'b', 'c'], write_converters: write_converters)
str # => "a,b,c\n"
```

--------------------------------

### CSV Parsing with `skip_lines` Option

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Demonstrates how to use the `skip_lines` option with `CSV.parse` to ignore lines starting with a specific character or pattern.

```APIDOC
## CSV.parse with skip_lines

### Description
Parses a CSV string, skipping lines that match the provided pattern.

### Method
`CSV.parse(string, **options)`

### Parameters
#### Options
- **skip_lines** (Regexp or String or nil) - Optional - Lines matching this pattern will be skipped.

### Request Example
```ruby
str = "# Comment\nfoo,0\nbar,1\nbaz,2\n# Another comment\n"

# Using a Regexp:
ary = CSV.parse(str, skip_lines: /^#/) 
# => [["foo", "0"], ["bar", "1"], ["baz", "2"]]

# Using a String:
ary = CSV.parse(str, skip_lines: '#')
# => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
```

### Error Handling
Raises an exception if `skip_lines` is not a Regexp, String, or nil.
```

--------------------------------

### Get the IO path

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

The `path` method returns the path of the underlying IO object if it responds to `path`. This is useful for identifying the source file.

```ruby
def path
  @io.path if @io.respond_to?(:path)
end
```

--------------------------------

### CSV Initialization with Options

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Initializes a new CSV object with specified options. Options are fixed after creation.

```ruby
def new(data = $stdout, **options)
  # ... implementation details ...
end
```

--------------------------------

### Initialize UnoptimizedStringIO

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser/UnoptimizedStringIO.html

Creates a new instance wrapping a string in a StringIO object with binary encoding.

```ruby
def initialize(string)
  @io = StringIO.new(string, "rb:#{string.encoding}")
end
```

--------------------------------

### Initialize CSV with Data

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/Object.html

Demonstrates basic CSV parsing by passing a string to the CSV constructor and reading the data. This is useful for simple CSV strings.

```ruby
CSV("CSV,data").read
  #=> [["CSV", "data"]]

```

--------------------------------

### CSV Gets Alias

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

An alias for the `shift` method.

```APIDOC
## CSV.gets (Alias for shift)

### Description
Alias for the `shift` method.

### Method
GET

### Endpoint
`csv.gets`
```

--------------------------------

### Apply header converters

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Demonstrates various ways to apply header converters including built-in symbols, lists, and custom Procs.

```ruby
str = <<-EOT
Name,Value
foo,0
bar,1
baz,2
EOT
# With no header converter
table = CSV.parse(str, headers: true)
table.headers # => ["Name", "Value"]
```

```ruby
table = CSV.parse(str, headers: true, header_converters: :downcase)
table.headers # => ["name", "value"]
```

```ruby
header_converters = [:downcase, :symbol]
table = CSV.parse(str, headers: true, header_converters: header_converters)
table.headers # => [:name, :value]
```

```ruby
upcase_converter = proc {|field| field.upcase }
table = CSV.parse(str, headers: true, header_converters: upcase_converter)
table.headers # => ["NAME", "VALUE"]
```

--------------------------------

### Initialize CSV without headers

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Demonstrates CSV initialization when the headers option is not provided.

```ruby
str = <<-EOT
Name,Count
foo,0
bar,1
bax,2
EOT
csv = CSV.new(str)
csv # => #<CSV io_type:StringIO encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
csv.headers # => nil
csv.shift # => ["Name", "Count"]
```

--------------------------------

### GET /csv/read

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Reads the remaining rows from the CSV source.

```APIDOC
## GET /csv/read

### Description
Forms the remaining rows from the CSV into a CSV::Table object if headers are in use, or an Array of Arrays otherwise.

### Method
GET

### Endpoint
/csv/read

### Response
#### Success Response (200)
- **data** (array/csv_table) - The parsed rows from the CSV source.
```

--------------------------------

### Prepare File for CSV Parsing

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Create a file with CSV content for testing file-based parsing methods.

```ruby
string = "foo,0\nbar,1\nbaz,2\n"
path = 't.csv'
File.write(path, string)
```

--------------------------------

### GET /csv/headers

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Retrieves the headers configuration or parsed headers.

```APIDOC
## GET /csv/headers

### Description
Returns the value that determines whether headers are used or the parsed headers themselves.

### Method
GET

### Endpoint
/csv/headers

### Response
#### Success Response (200)
- **headers** (object/nil) - The headers configuration or nil if not set.
```

--------------------------------

### GET /csv/eof

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Checks if the end of the CSV file has been reached.

```APIDOC
## GET /csv/eof

### Description
Returns true if the end of the CSV data has been reached, false otherwise.

### Method
GET

### Response
#### Success Response (200)
- **eof** (boolean) - True if at end of file.
```

--------------------------------

### Access Built-in Converter Lists

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Illustrates how to retrieve the predefined converter lists, :numeric and :all, from CSV::Converters. These provide common sets of conversion rules.

```ruby
CSV::Converters[:numeric] # => [:integer, :float]
CSV::Converters[:all] # => [:date_time, :numeric]
```

--------------------------------

### GET /csv/each

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Iterates over each row in the CSV data source.

```APIDOC
## GET /csv/each

### Description
Calls the provided block with each successive row of the CSV data. The source must be opened for reading.

### Method
GET

### Response
#### Success Response (200)
- **row** (array/CSV::Row) - The current row being processed.
```

--------------------------------

### GET /table/by_col

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Table.html

Returns a duplicate of the table in column mode.

```APIDOC
## GET /table/by_col

### Description
Creates and returns a duplicate CSV::Table object set to column mode. Useful for chaining operations without modifying the original table's mode.

### Response
#### Success Response (200)
- **table** (CSV::Table) - A duplicate table instance in column mode.
```

--------------------------------

### Initialize CSV with string headers

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Parses a string to generate column headers.

```ruby
str = <<-EOT
foo,0
bar,1
bax,2
EOT
csv = CSV.new(str, headers: 'Name,Count')
csv
csv.headers # => ["Name", "Count"]
csv.shift # => #<CSV::Row "Name":"bar" "Count":"1">
```

--------------------------------

### GET /csv/header_row?

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Checks if the CSV is configured to use header rows.

```APIDOC
## GET /csv/header_row?

### Description
Returns a boolean indicating whether headers are used for parsing.

### Method
GET

### Endpoint
/csv/header_row?

### Response
#### Success Response (200)
- **result** (boolean) - True if headers are used, false otherwise.
```

--------------------------------

### CSV Initialization

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Initializes a new CSV object. Raises ArgumentError if nil is provided as data.

```APIDOC
## CSV.new

### Description
Initializes a new CSV object with the provided data and various options.
Raises `ArgumentError` if `data` is `nil`.

### Method
`CSV.new(data, **options)`

### Parameters
- **data**: The data to parse, can be a String or an IO object.
- **col_sep** (String) - Column separator (default: ",")
- **row_sep** (String or Symbol) - Row separator (default: :auto)
- **quote_char** (String) - Quote character (default: '"')
- **field_size_limit** (Integer) - Maximum field size (default: nil)
- **converters** (Array or Symbol) - Field converters (default: nil)
- **unconverted_fields** (Boolean) - Keep unconverted fields (default: nil)
- **headers** (Boolean or Array) - Treat first row as headers (default: false)
- **return_headers** (Boolean) - Return headers as part of the data (default: false)
- **write_headers** (Boolean) - Write headers when generating CSV (default: nil)
- **header_converters** (Array or Symbol) - Header converters (default: nil)
- **skip_blanks** (Boolean) - Skip blank lines (default: false)
- **force_quotes** (Boolean) - Force quoting of all fields (default: false)
- **skip_lines** (Regexp) - Skip lines matching the regex (default: nil)
- **liberal_parsing** (Boolean) - Enable liberal parsing (default: false)
- **internal_encoding** (String) - Internal encoding (default: nil)
- **external_encoding** (String) - External encoding (default: nil)
- **encoding** (String) - Encoding for input and output (default: nil)
- **nil_value** (String) - Value to represent nil (default: nil)
- **empty_value** (String) - Value to represent empty fields (default: "")
- **quote_empty** (Boolean) - Quote empty fields (default: true)
- **write_converters** (Array or Symbol) - Converters for writing (default: nil)
- **write_nil_value** (String) - Nil value for writing (default: nil)
- **write_empty_value** (String) - Empty value for writing (default: "")
- **strip** (Boolean) - Strip whitespace from fields (default: false)

### Request Example
```ruby
CSV.new(nil)
```

### Response
#### Success Response (200)
Returns a new CSV object.

#### Response Example
```ruby
#<CSV io_type:StringIO encoding:UTF-8 col_sep:"," row_sep:"\n" quote_char:"\""></CSV>
```

#### Error Response
- **ArgumentError**: Raised if `data` is `nil`.
```

--------------------------------

### GET /csv/header_row

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Checks if the next row to be read is a header row.

```APIDOC
## GET /csv/header_row

### Description
Returns true if the next row to be read is a header row, false otherwise.

### Method
GET

### Response
#### Success Response (200)
- **is_header** (boolean) - True if the next row is a header.
```

--------------------------------

### Initialize CSV with nil

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Attempting to initialize a CSV object with nil raises an ArgumentError.

```ruby
CSV.new(nil)
```

--------------------------------

### CSV::InputsScanner Public Instance Methods

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser/InputsScanner.html

Documentation for the public instance methods of CSV::InputsScanner.

```APIDOC
### Public Instance Methods

each_line(row_separator) click to toggle source

``` ruby
# File csv/parser.rb, line 96
def each_line(row_separator)
  buffer = nil
  input = @scanner.rest
  position = @scanner.pos
  offset = 0
  n_row_separator_chars = row_separator.size
  while true
    input.each_line(row_separator) do |line|
      @scanner.pos += line.bytesize
      if buffer
        if n_row_separator_chars == 2 and
          buffer.end_with?(row_separator[0]) and
          line.start_with?(row_separator[1])
          buffer << line[0]
          line = line[1..-1]
          position += buffer.bytesize + offset
          @scanner.pos = position
          offset = 0
          yield(buffer)
          buffer = nil
          next if line.empty?
        else
          buffer << line
          line = buffer
          buffer = nil
        end
      end
      if line.end_with?(row_separator)
        position += line.bytesize + offset
        @scanner.pos = position
        offset = 0
        yield(line)
      else
        buffer = line
      end
    end
    break unless read_chunk
    input = @scanner.rest
    position = @scanner.pos
    offset = -buffer.bytesize if buffer
  end
  yield(buffer) if buffer
end
```

eos?() click to toggle source

``` ruby
# File csv/parser.rb, line 163
def eos?
  @scanner.eos?
end
```

keep_back() click to toggle source

``` ruby
# File csv/parser.rb, line 181
def keep_back
  start, buffer = @keeps.pop
  if buffer
    string = @scanner.string
    keep = string.byteslice(start, string.bytesize - start)
    if keep and not keep.empty?
      @inputs.unshift(StringIO.new(keep))
      @last_scanner = false
    end
    @scanner = StringScanner.new(buffer)
  else
    @scanner.pos = start
  end
  read_chunk if @scanner.eos?
end
```

keep_drop() click to toggle source

``` ruby
# File csv/parser.rb, line 197
def keep_drop
  @keeps.pop
end
```

keep_end() click to toggle source

``` ruby
# File csv/parser.rb, line 171
def keep_end
  start, buffer = @keeps.pop
  keep = @scanner.string.byteslice(start, @scanner.pos - start)
  if buffer
    buffer << keep
    keep = buffer
  end
  keep
end
```

keep_start() click to toggle source

``` ruby
# File csv/parser.rb, line 167
def keep_start
  @keeps.push([@scanner.pos, nil])
end
```

rest() click to toggle source

``` ruby
# File csv/parser.rb, line 201
def rest
  @scanner.rest
end
```

scan(pattern) click to toggle source

``` ruby
# File csv/parser.rb, line 140
def scan(pattern)
  value = @scanner.scan(pattern)
  return value if @last_scanner

  if value
    read_chunk if @scanner.eos?
    return value
  else
    nil
  end
end
```

scan_all(pattern) click to toggle source

``` ruby
# File csv/parser.rb, line 152
def scan_all(pattern)
  value = @scanner.scan(pattern)
  return value if @last_scanner

  return nil if value.nil?
  while @scanner.eos? and read_chunk and (sub_value = @scanner.scan(pattern))
    value << sub_value
  end
  value
end
```

```

--------------------------------

### Initialize CSV with Block for Conditional Logic

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/Object.html

Shows how to use a block with the CSV constructor to perform operations on the parsed data. The return value of the block becomes the return value of the CSV call. Useful for checking conditions on parsed CSV content.

```ruby
CSV("CSV,data") { |c|
  c.read.any? { |a| a.include?("data") }
} #=> true

CSV("CSV,data") { |c|
  c.read.any? { |a| a.include?("zombies") }
} #=> false

```

--------------------------------

### Initialize CSV::Writer

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Writer.html

Initializes a new CSV::Writer instance. Prepares the header if write_headers option is true. This is an internal class and should not be used directly.

```ruby
def initialize(output, options)
  @output = output
  @options = options
  @lineno = 0
  @fields_converter = nil
  prepare
  if @options[:write_headers] and @headers
    self << @headers
  end
  @fields_converter = @options[:fields_converter]
end
```

--------------------------------

### GET /csv/converters

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Returns an array containing the currently active field converters.

```APIDOC
## GET /csv/converters

### Description
Returns an Array containing field converters currently registered for the CSV instance.

### Method
GET

### Response
#### Success Response (200)
- **converters** (array) - List of active converter names or procs.
```

--------------------------------

### Initialize CSV::Parser

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser.html

Initializes a new CSV::Parser instance. This is an internal class and should not be used directly. It sets up input, options, and prepares for parsing.

```ruby
def initialize(input, options)
  @input = input
  @options = options
  @samples = []

  prepare
end
```

--------------------------------

### Get Default Converters

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Retrieves the default value for the converters option, which is nil.

```ruby
CSV::DEFAULT_OPTIONS.fetch(:converters) # => nil

```

--------------------------------

### Initialize CSV::Table

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Table.html

Constructs a new CSV::Table from an array of CSV::Row objects.

```ruby
# File csv/table.rb, line 31
def initialize(array_of_rows, headers: nil)
  @table = array_of_rows
  @headers = headers
  unless @headers
    if @table.empty?
      @headers = []
    else
      @headers = @table.first.headers
    end
  end

  @mode  = :col_or_row
end
```

--------------------------------

### Initialize CSV with array headers

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Uses the provided array elements as column headers.

```ruby
str = <<-EOT
foo,0
bar,1
bax,2
EOT
csv = CSV.new(str, headers: ['Name', 'Count'])
csv
csv.headers # => ["Name", "Count"]
csv.shift # => #<CSV::Row "Name":"bar" "Count":"1">
```

--------------------------------

### Get default row_sep

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Retrieve the default row separator used by the CSV library.

```ruby
CSV::DEFAULT_OPTIONS.fetch(:row_sep) # => :auto

```

--------------------------------

### Initialize CSV with boolean or symbol headers

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Treats the first row of data as headers when set to true or :first_row.

```ruby
str = <<-EOT
Name,Count
foo,0
bar,1
bax,2
EOT
csv = CSV.new(str, headers: true)
csv # => #<CSV io_type:StringIO encoding:UTF-8 lineno:2 col_sep:"," row_sep:"\n" quote_char:"\"" headers:["Name", "Count"]>
csv.headers # => ["Name", "Count"]
csv.shift # => #<CSV::Row "Name":"bar" "Count":"1">
```

--------------------------------

### Get remaining input in CSV::Parser::InputsScanner

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser/InputsScanner.html

Returns the remaining data in the scanner.

```ruby
def rest
  @scanner.rest
end
```

--------------------------------

### Get Default Unconverted Fields Setting

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Retrieves the default value for the unconverted_fields option, which is nil.

```ruby
CSV::DEFAULT_OPTIONS.fetch(:unconverted_fields) # => nil

```

--------------------------------

### CSV Parsing - File Input

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Explains how to parse CSV data from a file using its path with `CSV.read`, `CSV.foreach`, and `CSV.table`.

```APIDOC
## CSV Parsing - File Input

This section covers parsing CSV data when the input is a file.

### `CSV.read(path)`

Reads the entire content of a CSV file and returns it as an Array of Arrays.

**Parameters**:
- `path` (String) - The file path to the CSV file.

**Returns**:
- Array<Array<String>> - An array where each inner array represents a row of CSV data.

**Example**:
```ruby
# Assuming 't.csv' contains:
# foo,0
# bar,1
# baz,2
CSV.read('t.csv') # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
```

### `CSV.foreach(path)`

Iterates over each row of a CSV file, passing each row to a block.

**Parameters**:
- `path` (String) - The file path to the CSV file.
- `block` - A block that accepts a row (Array<String>) as an argument.

**Example**:
```ruby
CSV.foreach('t.csv') do |row|
  p row
end
# Output:
# ["foo", "0"]
# ["bar", "1"]
# ["baz", "2"]
```

### `CSV.table(path)`

Reads the entire content of a CSV file and returns it as a `CSV::Table` object, which is useful for CSVs with headers.

**Parameters**:
- `path` (String) - The file path to the CSV file.

**Returns**:
- CSV::Table - A `CSV::Table` object representing the CSV data.

**Example**:
```ruby
CSV.table('t.csv') # => #<CSV::Table mode:col_or_row row_count:3>
```
```

--------------------------------

### Get Headers - CSV::Parser

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser.html

Returns the parsed headers of the CSV data. This is an internal method.

```ruby
def headers
  @headers
end
```

--------------------------------

### Open CSV with path or file

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Creating a CSV object using either a file path or an open File object.

```ruby
csv = CSV.open(path)
csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
```

```ruby
csv = CSV.open(File.open(path))
csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
```

--------------------------------

### CSV::InputsScanner Class Overview

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser/InputsScanner.html

Provides an overview of the CSV::InputsScanner class, its purpose, and its core functionalities.

```APIDOC
## CSV::InputsScanner

CSV::InputsScanner receives IO inputs, encoding and the chunk_size. It also controls the life cycle of the object with its methods `keep_start`, `keep_end`, `keep_back`, `keep_drop`.

CSV::InputsScanner.scan() tries to match with pattern at the current position. If there's a match, the scanner advances the “scan pointer” and returns the matched string. Otherwise, the scanner returns nil.

CSV::InputsScanner.rest() returns the “rest” of the string (i.e. everything after the scan pointer). If there is no more data (eos? = true), it returns “”.

```

--------------------------------

### Get Default Strip Option

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Retrieves the default value for the `strip` option from `CSV::DEFAULT_OPTIONS`, which is `false`.

```ruby
CSV::DEFAULT_OPTIONS.fetch(:strip) # => false
```

--------------------------------

### GET values_at

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Table.html

Retrieves specific rows or columns from the CSV table based on provided indices or headers.

```APIDOC
## GET values_at

### Description
Retrieves data from the CSV table. If the access mode is :row or :col_or_row and arguments are Integers or Ranges, it returns rows as CSV::Row objects. Otherwise, it returns columns data as arrays.

### Method
GET

### Parameters
#### Query Parameters
- **indices_or_headers** (Integer, Range, or String) - Required - A variable number of arguments representing row indices, ranges of indices, or column headers.

### Response
#### Success Response (200)
- **result** (Array) - An array of CSV::Row objects or an array of arrays containing column data.
```

--------------------------------

### Define Converter Lists in Ruby

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Demonstrates how to create and use converter lists, which are arrays that can contain procs, names of stored converters, or nested lists. These are used for organizing multiple conversion rules.

```ruby
numeric_converters = [:integer, :float]
date_converters = [:date, :date_time]
[numeric_converters, strip_converter]
[strip_converter, date_converters, :float]
```

--------------------------------

### Instance Method: match?

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/MatchP.html

The match? method checks if the object matches a given pattern using the =~ operator.

```APIDOC
## Instance Method: match?

### Description
Checks if the current object matches the provided pattern.

### Method
Instance Method

### Parameters
- **pattern** (Object) - Required - The pattern to match against the object.

### Request Example
```ruby
csv_match_p.match?(/pattern/)
```

### Response
- **result** (Boolean) - Returns true if the pattern matches, false otherwise.
```

--------------------------------

### Get CSV Column Separator

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Returns the encoded column separator used for parsing and writing. Defaults to a comma.

```ruby
CSV.new('').col_sep # => ","

```

```ruby

               # File csv.rb, line 1821
def col_sep
  parser.column_separator
end
            

```

--------------------------------

### CSV Configuration Options

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Documentation for the row_sep and col_sep options used in CSV parsing and generation.

```APIDOC
## CSV Configuration Options

### Description
This section covers the configuration options for customizing CSV data processing, specifically row and column separators.

### Parameters
#### Request Body
- **row_sep** (String or Symbol) - Optional - Specifies the row separator. Defaults to :auto. Can be a custom string or :auto for auto-discovery.
- **col_sep** (String) - Optional - Specifies the field separator. Defaults to ",". Must be 1 or more characters for parsing.

### Notes
- **row_sep**: When set to :auto, the parser attempts to detect line endings (\r\n, \n, or \r). If not found, it defaults to $INPUT_RECORD_SEPARATOR.
- **col_sep**: Must be a string. Providing an empty string for parsing will raise an ArgumentError.
```

--------------------------------

### Get Default Nil Value Option

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Retrieves the default value for the `nil_value` option from `CSV::DEFAULT_OPTIONS`, which is `nil`.

```ruby
CSV::DEFAULT_OPTIONS.fetch(:nil_value) # => nil
```

--------------------------------

### Get Default Liberal Parsing Option

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Retrieves the default value for the `liberal_parsing` option from `CSV::DEFAULT_OPTIONS`, which is `false`.

```ruby
CSV::DEFAULT_OPTIONS.fetch(:liberal_parsing) # => false
```

--------------------------------

### Get Default Quote Character

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Retrieves the default character used for quoting fields in CSV parsing and generation.

```ruby
CSV::DEFAULT_OPTIONS.fetch(:quote_char) # => "\"" (double quote)
```

--------------------------------

### Create CSV Instance with Integer Field Converter

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Initializes a CSV instance with a string and applies the :integer converter. The converter is active for subsequent reads.

```ruby
string = "foo,0\nbar,1\nbaz,2\n"
csv = CSV.new(string, converters: :integer)
# Field converters in effect:
csv.converters # => [:integer]
csv.read # => [["foo", 0], ["bar", 1], ["baz", 2]]
```

--------------------------------

### Get Default Field Size Limit

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Retrieves the default value for the field size limit, which is nil, indicating no limit.

```ruby
CSV::DEFAULT_OPTIONS.fetch(:field_size_limit) # => nil

```

--------------------------------

### Initialize CSV::FieldsConverter

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/FieldsConverter.html

Initializes the converter instance with options for nil and empty value handling.

```ruby
def initialize(options={})
  @converters = []
  @nil_value = options[:nil_value]
  @empty_value = options[:empty_value]
  @empty_value_is_empty_string = (@empty_value == "")
  @accept_nil = options[:accept_nil]
  @builtin_converters = options[:builtin_converters]
  @need_static_convert = need_static_convert?
end
```

--------------------------------

### GET /table/index_or_header

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Table.html

Retrieves rows by index/range or column values by header name, depending on the current table access mode.

```APIDOC
## GET /table/index_or_header

### Description
Accesses table data. If the mode is :row or :col_or_row with an Integer/Range, it returns rows. Otherwise, it returns column values by header.

### Parameters
#### Path Parameters
- **index_or_header** (Integer|Range|String) - Required - The index or range for row access, or the header name for column access.

### Response
#### Success Response (200)
- **result** (Array|CSV::Row|nil) - The requested row(s) or column values.
```

--------------------------------

### Initialize CSV::Parser::InputsScanner

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser/InputsScanner.html

Initializes a new scanner instance with inputs, encoding, and an optional chunk size.

```ruby
def initialize(inputs, encoding, chunk_size: 8192)
  @inputs = inputs.dup
  @encoding = encoding
  @chunk_size = chunk_size
  @last_scanner = @inputs.empty?
  @keeps = []
  read_chunk
end
```

--------------------------------

### Generate CSV with CSV.generate

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Demonstrates the usage of CSV.generate to create a CSV string. Note that passing an integer will raise a TypeError.

```ruby
CSV.generate(0)
```

```ruby
def generate(str=nil, **options)
  encoding = options[:encoding]
  # add a default empty String, if none was given
  if str
    str = StringIO.new(str)
    str.seek(0, IO::SEEK_END)
    str.set_encoding(encoding) if encoding
  else
    str = +""
    str.force_encoding(encoding) if encoding
  end
  csv = new(str, **options) # wrap
  yield csv         # yield for appending
  csv.string        # return final String
end
```

--------------------------------

### Get Line Number - CSV::Parser

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser.html

Returns the current line number being processed in the CSV data. This is an internal method.

```ruby
def lineno
  @lineno
end
```

--------------------------------

### Get Current Line - CSV::Parser

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser.html

Returns the content of the current line being processed. This is an internal method that delegates to `last_line`.

```ruby
def line
  last_line
end
```

--------------------------------

### CSV generation without write_headers

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Shows how to open a CSV file for writing with headers defined, but without explicitly enabling `write_headers`. The header row will not be included in the output file.

```ruby
file_path = 't.csv'
CSV.open(file_path,'w',
    :headers => ['Name','Value']
  ) do |csv|
    csv << ['foo', '0']
end
CSV.open(file_path) do |csv|
  csv.shift
end # => ["foo", "0"]
```

--------------------------------

### Get Row Separator - CSV::Parser

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser.html

Returns the character or string used to separate rows in the CSV data. This is an internal method.

```ruby
def row_separator
  @row_separator
end
```

--------------------------------

### Skip blank lines in CSV

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Demonstrates how to ignore blank lines during parsing.

```ruby
str = <<-EOT
foo,0

bar,1
baz,2

,
EOT
```

```ruby
ary = CSV.parse(str)
ary # => [["foo", "0"], [], ["bar", "1"], ["baz", "2"], [], [nil, nil]]
```

```ruby
ary = CSV.parse(str, skip_blanks: true)
ary # => [["foo", "0"], ["bar", "1"], ["baz", "2"], [nil, nil]]
```

```ruby
ary = CSV.parse(str, skip_blanks: :foo)
ary # => [["foo", "0"], ["bar", "1"], ["baz", "2"], [nil, nil]]
```

--------------------------------

### Get Field Size Limit - CSV::Parser

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser.html

Returns the maximum allowed size for a single field in the CSV. This is an internal method.

```ruby
def field_size_limit
  @field_size_limit
end
```

--------------------------------

### Initialize CSV::Row

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Row.html

Constructs a new CSV::Row. Use this when creating rows manually. It handles cases where headers and fields have different sizes by padding with nil.

```ruby
def initialize(headers, fields, header_row = false)
  @header_row = header_row
  headers.each { |h| h.freeze if h.is_a? String }

  # handle extra headers or fields
  @row = if headers.size >= fields.size
    headers.zip(fields)
  else
    fields.zip(headers).each(&:reverse!)
  end
end
```

--------------------------------

### Get Column Separator - CSV::Parser

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser.html

Returns the configured column separator character used in the CSV data. This is an internal method.

```ruby
def column_separator
  @column_separator
end
```

--------------------------------

### CSV Constructor Implementation

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/Object.html

The source code for the CSV constructor method, which delegates to `CSV.instance`. This is the underlying implementation of the CSV object creation.

```ruby
               # File csv.rb, line 2653
def CSV(*args, &block)
  CSV.instance(*args, &block)
end
            
```

--------------------------------

### Generate CSV from Scratch

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Creates a new CSV string from an empty state by adding rows within a block.

```ruby
output_string = CSV.generate do |csv|
  csv << ['foo', 0]
  csv << ['bar', 1]
  csv << ['baz', 2]
end
output_string # => "foo,0\nbar,1\nbaz,2\n"
```

--------------------------------

### Open CSV with block

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Using a block with CSV.open to automatically handle the CSV object.

```ruby
csv = CSV.open(path) {|csv| p csv}
csv # => #<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
```

```ruby
#<CSV io_type:File io_path:"t.csv" encoding:UTF-8 lineno:0 col_sep:"," row_sep:"\n" quote_char:"\"">
```

--------------------------------

### Parse CSV with Default Skip Lines

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Parses a CSV string using the default behavior where comment lines starting with '#' are included.

```ruby
str = "# Comment\nfoo,0\nbar,1\nbaz,2\n# Another comment\n"
ary = CSV.parse(str)
ary # => [["# Comment"], ["foo", "0"], ["bar", "1"], ["baz", "2"], ["# Another comment"]]
```

--------------------------------

### CSV::InputsScanner Public Class Methods

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Parser/InputsScanner.html

Documentation for the public class methods of CSV::InputsScanner.

```APIDOC
### Public Class Methods

new(inputs, encoding, chunk_size: 8192) click to toggle source

``` ruby
# File csv/parser.rb, line 87
def initialize(inputs, encoding, chunk_size: 8192)
  @inputs = inputs.dup
  @encoding = encoding
  @chunk_size = chunk_size
  @last_scanner = @inputs.empty?
  @keeps = []
  read_chunk
end
```

```

--------------------------------

### Get IO Stat

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Retrieves the stat object for the underlying IO object, if supported. This provides file system information about the data source.

```ruby
def stat(*args)
  raise NotImplementedError unless @io.respond_to?(:stat)
  @io.stat(*args)
end
```

--------------------------------

### Get Row Separator

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Returns the encoded string used to separate rows in the CSV data. This is used for both parsing and writing CSV files.

```ruby
CSV.new('').row_sep
```

```ruby
def row_sep
  parser.row_separator
end
```

--------------------------------

### POST /CSV::Table/new

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV/Table.html

Constructs a new CSV::Table object from an array of rows.

```APIDOC
## POST /CSV::Table/new

### Description
Constructs a new CSV::Table from an array of CSV::Row objects.

### Parameters
#### Request Body
- **array_of_rows** (Array) - Required - An array of CSV::Row objects.
- **headers** (Array) - Optional - An array of headers. If not provided, headers are fetched from the first row.
```

--------------------------------

### CSV Parsing - String Input

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Demonstrates how to parse CSV data directly from a String object using `CSV.parse` and `CSV.parse_line`, as well as the `String#parse_csv` instance method.

```APIDOC
## CSV Parsing - String Input

This section covers parsing CSV data when the input is provided as a String.

### `CSV.parse(string)`

Parses the entire CSV data from a string and returns it as an Array of Arrays.

**Parameters**:
- `string` (String) - The CSV data to parse.

**Returns**:
- Array<Array<String>> - An array where each inner array represents a row of CSV data.

**Example**:
```ruby
string = "foo,0\nbar,1\nbaz,2\n"
CSV.parse(string) # => [["foo", "0"], ["bar", "1"], ["baz", "2"]]
```

### `CSV.parse_line(string)`

Parses only the first line (row) of CSV data from a string.

**Parameters**:
- `string` (String) - The CSV data to parse.

**Returns**:
- Array<String> - An array representing the first row of CSV data.

**Example**:
```ruby
string = "foo,0\nbar,1\nbaz,2\n"
CSV.parse_line(string) # => ["foo", "0"]
```

### `String#parse_csv`

An instance method added to String that parses the first line of CSV data.

**Parameters**:
- None

**Returns**:
- Array<String> - An array representing the first row of CSV data.

**Example**:
```ruby
string = "foo,0\nbar,1\nbaz,2\n"
string.parse_csv # => ["foo", "0"]
```
```

--------------------------------

### Get Default Empty Value Option

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Retrieves the default value for the `empty_value` option from `CSV::DEFAULT_OPTIONS`, which is an empty string `""`.

```ruby
CSV::DEFAULT_OPTIONS.fetch(:empty_value) # => ""
```

--------------------------------

### CSV initialization with non-string quote_char

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Demonstrates that the quote_char option must be a string; providing a non-string value raises an ArgumentError.

```ruby
# Raises ArgumentError (:quote_char has to be nil or a single character String)
CSV.new('', quote_char: :foo)
```

--------------------------------

### Get CSV headers

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

The `headers` method retrieves the headers used for parsing. It returns `nil` if no headers are defined or if the `headers` option was set to `false`.

```ruby
def headers
  if @writer
    @writer.headers
  else
    parsed_headers = parser.headers
    return parsed_headers if parsed_headers
    raw_headers = @parser_options[:headers]
    raw_headers = nil if raw_headers == false
    raw_headers
  end
end
```

--------------------------------

### Add Multiple Converters to CSV Instance

Source: https://ruby-doc.org/stdlib-3.0.0/libdoc/csv/rdoc/CSV.html

Shows how to sequentially add multiple field converters (:integer and :date) to a CSV instance using the `convert` method. The `converters` method then lists all active converters.

```ruby
csv = CSV.new('0,1,2')
csv.converters # => []
csv.convert(:integer)
csv.converters # => [:integer]
csv.convert(:date)
csv.converters # => [:integer, :date]
```
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