### View Code for Multiple Form Inputs (ERB)

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Example of how to structure a form using `fields_for` to combine multiple input values for a single scope, such as filtering by distance and city.

```erb
<%# app/views/students/index.html.erb
  Add a `fields_for` helper to your filterrific form:
%>
<%= form_for @filterrific do |f| %>
  ...
  <div>
    Distance
    <%= f.fields_for :with_distance do |with_distance_fields|
      %><%= with_distance_fields.text_field :max_distance %><%
      %><%= with_distance_fields.text_field :city %><%
    end %>
  </div>
  ...

```

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

### Add Filterrific Gem to Gemfile

Source: http://filterrific.clearcove.ca/

To install Filterrific, add the gem to your application's Gemfile.

```ruby
# Gemfile
gem 'filterrific'
```

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

### Initialize Filterrific in Controller

Source: http://filterrific.clearcove.ca/pages/action_controller_api.html

Use `initialize_filterrific` in your controller's index action to set up filterrific. It accepts the model class, params, and various options for customization, including select options, persistence ID, default parameters, available filters, and sanitization. Ensure `||= return` is used for proper redirect on reset.

```ruby
class StudentsController < ApplicationController

  def index
    # Initialize filterrific with the following params:
    # * `Student` is the ActiveRecord based model class.
    # * `params[:filterrific]` are any params submitted via web request.
    #   If they are blank, filterrific will try params persisted in the session
    #   next. If those are blank, too, filterrific will use the model's default
    #   filter settings.
    # * Options:
    #     * select_options: You can store any options for `<select>` inputs in
    #       the filterrific form here. In this example, the `#options_for_...`
    #       methods return arrays that can be passed as options to `f.select`
    #       These methods are defined in the model.
    #     * persistence_id: optional, defaults to "<controller>#<action>" string
    #       to isolate session persistence of multiple filterrific instances.
    #       Override this to share session persisted filter params between
    #       multiple filterrific instances. Set to `false` to disable session
    #       persistence.
    #     * default_filter_params: optional, to override model defaults
    #     * available_filters: optional, to further restrict which filters are
    #       in this filterrific instance.
    #     * sanitize_params: optional, defaults to `true`. If true, all filterrific
    #       params will be sanitized to prevent reflected XSS attacks.
    # This method also persists the params in the session and handles resetting
    # the filterrific params.
    # In order for reset_filterrific to work, it's important that you add the
    # `or return` bit after the call to `initialize_filterrific`. Otherwise the
    # redirect will not work.
    @filterrific = initialize_filterrific(
      Student,
      params[:filterrific],
      select_options: {
        sorted_by: Student.options_for_sorted_by,
        with_country_id: Country.options_for_select,
      },
      persistence_id: "shared_key",
      default_filter_params: {},
      available_filters: [:sorted_by, :with_country_id],
      sanitize_params: true,
    ) || return
    # Get an ActiveRecord::Relation for all students that match the filter settings.
    # You can paginate with will_paginate or kaminari.
    # NOTE: filterrific_find returns an ActiveRecord Relation that can be
    # chained with other scopes to further narrow down the scope of the list,
    # e.g., to apply permissions or to hard coded exclude certain types of records.
    @students = @filterrific.find.page(params[:page])

    # Respond to html for initial page load and to js for AJAX filter updates.
    respond_to do |format|
      format.html
      format.js
    end

  # Recover from invalid param sets, e.g., when a filter refers to the
  # database id of a record that doesn’t exist any more.
  # In this case we reset filterrific and discard all filter params.
  rescue ActiveRecord::RecordNotFound => e
    # There is an issue with the persisted param_set. Reset it.
    puts "Had to reset filterrific params: #{e.message}"
    redirect_to(reset_filterrific_url(format: :html)) && return
  end

  ...

end

```

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

### Sorting Students by Created At

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Sorts students based on their creation timestamp. Includes the table name to prevent ambiguity when joining tables.

```ruby
direction = /desc$/.match?(sort_option) ? "desc" : "asc"
case sort_option.to_s
when /^created_at_/
  order("students.created_at #{direction}")
when /^name_/
  order("LOWER(students.last_name) #{direction}, LOWER(students.first_name) #{direction}")
when /^country_name_/
  order("LOWER(countries.name) #{direction}").includes(:country).references(:country)
else
  raise(ArgumentError, "Invalid sort option: #{sort_option.inspect}")
end
```

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

### Basic Search Scope with LIKE Operator

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Implement a basic search functionality using SQL's LIKE operator. This scope is case-insensitive with MySQL but case-sensitive with PostgreSQL; downcasing is used for cross-database compatibility.

```ruby
scope :search_query, ->(query) {
  # Searches the students table on the 'first_name' and 'last_name' columns.
  # Matches using LIKE, automatically appends '%' to each term.
  # LIKE is case INsensitive with MySQL, however it is case
  # sensitive with PostGreSQL. To make it work in both worlds,
  # we downcase everything.
  return nil  if query.blank?

  # condition query, parse into individual keywords
  terms = query.downcase.split(/\s+/

  # replace "*" with "%" for wildcard searches,
  # append '%', remove duplicate '%'s
  terms = terms.map { |e|
    (e.tr("*", "%" ) + "%" ).gsub(/%+/,"%" )
  }
  # configure number of OR conditions for provision
  # of interpolation arguments. Adjust this if you
  # change the number of OR conditions.
  num_or_conds = 2
  where(
    terms.map { |_term|
      "(LOWER(students.first_name) LIKE ? OR LOWER(students.last_name) LIKE ?)"
    }.join(" AND "),
    *terms.map { |e| [e] * num_or_conds }.flatten,
  )
}
```

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

### Use Filterrific in Controller Index Action

Source: http://filterrific.clearcove.ca/

Initialize Filterrific in your controller's index action to handle filtering and pagination. Respond to HTML and JS formats.

```ruby
def index
  @filterrific = initialize_filterrific(
    Student,
    params[:filterrific]
  ) or return
  @students = @filterrific.find.page(params[:page])

  respond_to do |format|
    format.html
    format.js
  end
end
```

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

### Filter Students by All Given Roles (Ruby)

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Use this scope to find students who possess ALL of the specified roles. It constructs a complex SQL query using AREL to avoid duplicate records and potential issues with DISTINCT clauses.

```ruby
scope :with_all_role_ids, ->(role_ids) {
  # get a reference to the join table
  role_assignments = RoleAssignment.arel_table
  # get a reference to the filtered table
  students = Student.arel_table
  # let AREL generate a complex SQL query
  role_ids.map(&:to_i).inject(self) { |rel, role_id| 
    rel.where(
      RoleAssignment
        .where(role_assignments[:student_id].eq(students[:id]))
        .where(role_assignments[:role_id].eq(role_id))
        .exists,
    )
  }
}
```

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

### Provide Select Options for Filterrific

Source: http://filterrific.clearcove.ca/pages/active_record_model_api.html

Define a presenter method on a related model to provide options for a Filterrific select input. This method should return an array of arrays, where each inner array contains the display text and the corresponding value.

```ruby
def self.options_for_select
  order("LOWER(name)").map { |e| [e.name, e.id] }
end

```

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

### Include Filterrific jQuery Observers and Spinner

Source: http://filterrific.clearcove.ca/pages/action_view_api.html

Add this line to your `application.js` file to include the necessary jQuery behaviors for Filterrific form observers and the AJAX spinner, assuming you are using the asset pipeline.

```javascript
//= require filterrific/filterrific-jquery
```

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

### Filter by Date Range - Less Than (Ruby)

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Scope to filter records by a date column, excluding the specified reference time. Use this for the upper boundary of a semi-open interval.

```ruby
# always exclude the upper boundary for semi open intervals
scope :created_at_lt, ->(reference_time) {
  where("students.created_at < ?", reference_time)
}
```

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

### Student Model Definition

Source: http://filterrific.clearcove.ca/pages/example_application.html

Defines the Student model, including its attributes and its association with the Country model. This is the primary model used for filtering in the demo application.

```ruby
# app/models/student.rb
class Student < ActiveRecord::Base
  # db columns:
  # integer: id
  # string: first_name
  # string: last_name
  # text: email
  # integer: country_id
  # datetime: created_at

  belongs_to :country
end

```

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

### Apply Filterrific to ActiveRecord Model

Source: http://filterrific.clearcove.ca/pages/active_record_model_api.html

Apply the `filterrific` directive to your model to enable filtering. Define default filter parameters and list all available filters. This acts as a security measure, similar to `strong_params` for filter settings.

```ruby
class Student < ActiveRecord::Base

  # db columns:
  # integer: id
  # string: first_name
  # string: last_name
  # text: email
  # integer: country_id
  # datetime: created_at

  # This directive enables Filterrific for the Student class.
  # We define a default sorting by most recent sign up, and then
  # we make a number of filters available through Filterrific.
  filterrific(
    default_filter_params: { sorted_by: "created_at_desc" },
    available_filters: [
      :sorted_by,
      :search_query,
      :with_country_id,
      :with_created_at_gte,
    ],
  )

  # ActiveRecord association declarations
  belongs_to :country

  # Scope definitions. We implement all Filterrific filters through ActiveRecord
  # scopes. In this example we omit the implementation of the scopes for brevity.
  # Please see 'Scope patterns' for scope implementation details.
  scope :search_query, ->(query) {
    # Filters students whose name or email matches the query
    ...
  }
  scope :sorted_by, ->(sort_key) {
    # Sorts students by sort_key
    ...
  }
  scope :with_country_id, ->(country_ids) {
    # Filters students with any of the given country_ids
    ...
  }
  scope :with_created_at_gte, ->(ref_date) {
    ...
  }

  # This method provides select options for the `sorted_by` filter select input.
  # It is called in the controller as part of `initialize_filterrific`.
  def self.options_for_sorted_by
    [
      ["Name (a-z)", "name_asc"],
      ["Registration date (newest first)", "created_at_desc"],
      ["Registration date (oldest first)", "created_at_asc"],
      ["Country (a-z)", "country_name_asc"],
    ]
  end

end

```

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

### Filter Students with Comments

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Finds students who have at least one associated comment. Uses a SQL EXISTS subquery.

```ruby
scope :with_comments, -> {
  where(
    "EXISTS (SELECT 1 from comments WHERE students.id = comments.student_id)",
  )
}
```

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

### Filter Students Without Comments

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Finds students who have never posted a comment. Uses a SQL NOT EXISTS subquery.

```ruby
scope :without_comments, -> {
  where(
    %(NOT EXISTS (
      SELECT 1 FROM comments WHERE comments.student_id = students.id
    )),
  )
}
```

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

### Filter Students Without Given Roles (Ruby)

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

This scope finds students who DO NOT have any of the specified roles. It is similar to the `with_all_role_ids` scope but uses the `.not` operator to invert the existence check.

```ruby
scope :without_role_ids, ->(role_ids) {
  role_assignments = RoleAssignment.arel_table
  students = Student.arel_table
  where(
    RoleAssignment
      .where(role_assignments[:student_id].eq(students[:id]))
      .where(role_assignments[:role_id].in([*role_ids].map(&:to_i)))
      .exists
      .not,
  )
}
```

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

### Country Model Definition

Source: http://filterrific.clearcove.ca/pages/example_application.html

Defines the Country model, which represents countries and has a one-to-many association with the Student model. Some students may not be associated with a country.

```ruby
# app/models/country.rb
class Country < ActiveRecord::Base
  # db columns:
  # integer: id
  # string: name

  has_many :students
end

```

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

### Filter by Date Range - Greater Than or Equal (Ruby)

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Scope to filter records by a date column, including the specified reference time. Use this for the lower boundary of a semi-open interval.

```ruby
# always include the lower boundary for semi open intervals
scope :created_at_gte, ->(reference_time) {
  where("students.created_at >= ?", reference_time)
}
```

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

### Filter Students with Comments Since a Specific Time

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Finds students who have posted a comment after a given reference time. Uses a SQL EXISTS subquery with a date condition.

```ruby
scope :with_comments_since, ->(reference_time) {
  where([ 
          %( 
            EXISTS ( 
              SELECT 1 
                FROM comments 
               WHERE students.id = comments.student_id 
                 AND comments.created_at >= ?) 
          ), 
          reference_time, 
        ])
}
```

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

### Filter by Associated Table Column (Hash Syntax)

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Use this scope to filter records based on a column in an associated table using hash syntax. It requires joining the associated table.

```ruby
scope :with_country_name, ->(country_name) {
  where(country: { name: country_name }).joins(:country)
}
```

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

### Rendering Filtered Results Partial in Rails

Source: http://filterrific.clearcove.ca/pages/action_view_api.html

This partial renders the list of records. It's designed to be updated via AJAX. Use `page_entries_info` for pagination information and `will_paginate` for pagination controls.

```erb
<%# app/views/students/_list.html.erb %><div id="filterrific_results">  <div>    <%= page_entries_info students # provided by will_paginate %>  </div>  <table>    <tr>      <th>Name</th>      <th>Email</th>      <th>Country</th>      <th>Registered at</th>    </tr>    <% students.each do |student| %>      <tr>        <td><%= link_to(student.full_name, student_path(student)) %></td>        <td><%= student.email %></td>        <td><%= student.country_name %></td>        <td><%= student.decorated_created_at %></td>      </tr>    <% end %>  </table></div><%= will_paginate students # provided by will_paginate %>
```

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

### Filter Students with Any Role IDs

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Finds students who have any of the specified role IDs. This scope traverses a has_many :through association.

```ruby
scope :with_any_role_ids, ->(role_ids) {

```

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

### Sorting Scope Convention

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Define a scope for sorting records. The suggested naming convention is `sorted_by` to avoid potential collisions with ActiveRecord reserved names.

```ruby
scope :sorted_by, ->(sort_option) {

```

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

### Filterrific Sorted By Scope

Source: http://filterrific.clearcove.ca/pages/action_view_api.html

Define a `sorted_by` scope in your model to handle sorting logic. This scope determines how column headers are capitalized and maps them to the correct database order clause.

```ruby
scope :sorted_by, ->(sort_option) {
  direction = /desc$/.match?(sort_option) ? "desc" : "asc"
  case sort_option.to_s
  when /^name/
    order("LOWER(students.name) #{direction}")
  when /^email/
    order("LOWER(students.email) #{direction}")
  when /^country/
    order("LOWER(students.country) #{direction}")
  when /^registered_at/
    order("LOWER(students.decorated_created_at) #{direction}")
  else
    raise(ArgumentError, "Invalid sort option: #{sort_option.inspect}")
  end
}
```

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

### Filter by Associated Table Column (Sanitized SQL)

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Use this scope for more complex filtering needs, such as 'greater than' comparisons, by employing sanitized SQL snippets. It also requires joining the associated table.

```ruby
scope :with_country_name, ->(country_name) {
  where("countries.name = ?", country_name).joins(:country)
}
```

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

### Filterrific Form Helper in Rails View

Source: http://filterrific.clearcove.ca/pages/action_view_api.html

Use `form_for_filterrific` in your Rails view to create a form for filter settings. It automatically handles AJAX submission, spinners, and input name prefixes. Add the `filterrific-periodically-observed` class to text fields for live updates.

```erb
<%# app/views/students/index.html.erb %><h1>Students</h1><%#  Filterrific adds the `form_for_filterrific` view helper:  * adds dom id 'filterrific_filter'  * applies javascript behaviors:      * AJAX form submission on change      * AJAX spinner while AJAX request is being processed  * sets form_for options like :url, :method and input name prefix %> <%= form_for_filterrific @filterrific do |f| %>  <div>    Search    <%# give the search field the 'filterrific-periodically-observed' class for live updates %>    <%= f.text_field(      :search_query,      class: 'filterrific-periodically-observed'    ) %>  </div>  <div>    Country    <%= f.select(      :with_country_id,      @filterrific.select_options[:with_country_id],      { include_blank: '- Any -' }    ) %>  </div>  <div>    Registered after    <%= f.text_field(:with_created_at_gte, class: 'js-datepicker') %>  </div>  <div>    Sorted by    <%= f.select(:sorted_by, @filterrific.select_options[:sorted_by]) %>  </div>  <div>    <%= link_to(      'Reset filters',      reset_filterrific_url,    ) %>  </div>  <%# add an automated spinner to your form when the list is refreshed %>  <%= render_filterrific_spinner %> <% end %><%= render(  partial: 'students/list',  locals: { students: @students }) %>
```

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

### Updating Filtered List via AJAX in Rails

Source: http://filterrific.clearcove.ca/pages/action_view_api.html

This ERB template is used for JavaScript responses to update the student list. It renders the `_list.html.erb` partial and replaces the content of the `#filterrific_results` div.

```erb
<%# app/views/students/index.js.erb %><% js = escape_javascript(  render(partial: 'students/list', locals: { students: @students })) $("#filterrific_results").html("<%= js %>");
```

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

### Filterrific Sorting Link Helper

Source: http://filterrific.clearcove.ca/pages/action_view_api.html

Use `filterrific_sorting_link` in your view's table headers to create sortable links. This method toggles sort direction for attributes defined in the `sorted_by` scope.

```erb
<%# app/views/students/_list.html.erb %>
<div id="filterrific_results">

  <div>
    <%= page_entries_info students # provided by will_paginate %>
  </div>

  <table>
    <tr>
      <th><%= filterrific_sorting_link(@filterrific, :name) %></th>
      <th><%= filterrific_sorting_link(@filterrific, :email) %></th>
      <th><%= filterrific_sorting_link(@filterrific, :country) %></th>
      <th><%= filterrific_sorting_link(@filterrific, :registered_at) %></th>
    </tr>
    <% students.each do |student| %>
      <tr>
        <td><%= link_to(student.full_name, student_path(student)) %></td>
        <td><%= student.email %></td>
        <td><%= student.country_name %></td>
        <td><%= student.decorated_created_at %></td>
      </tr>
    <% end %>
  </table>
</div>

<%= will_paginate students # provided by will_paginate %>
```

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

### Add Filterrific to ActiveRecord Model

Source: http://filterrific.clearcove.ca/

Integrate Filterrific into your ActiveRecord model by calling the filterrific method and defining available filters.

```ruby
filterrific(
  default_filter_params: { sorted_by: 'created_at_desc' },
  available_filters:
    :sorted_by,
    :search_query,
    :with_country_id,
    :with_created_at_gte
)
# define ActiveRecord scopes for
# :search_query, :sorted_by, :with_country_id, and :with_created_at_gte
```

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

### Scope Definition for Multiple Form Inputs (Ruby)

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Defines a scope that accepts a hash of attributes, typically from multiple form inputs combined using `fields_for`. The `distance_attrs` hash is expected to contain keys like `:max_distance` and `:city`.

```ruby
scope :with_distance, ->(distance_attrs) {
  # `distance_attrs` is a hash with two keys:
  # {
  #   :max_distance => '10',
  #   :city => 'Vancouver',
  # }
  where(...)
}
```

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

### Filter by Column Values with ActiveRecord Scopes

Source: http://filterrific.clearcove.ca/pages/active_record_scope_patterns.html

Define scopes to filter records based on specific column values or foreign keys. The `[*column_ids]` expression ensures that single values are also handled as arrays.

```ruby
scope :with_country_id, ->(country_ids) {
  where(country_id: [*country_ids])
}

# filters on 'gender' attribute
scope :with_gender, ->(genders) {
  where(gender: [*genders])
}
```

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

### Disable AJAX Auto Submits with Filterrific Form

Source: http://filterrific.clearcove.ca/pages/action_view_api.html

Override the default form ID to disable automatic AJAX form submissions. Add `remote: true` if you still want AJAX, and include a submit button. Ensure no inputs have the `.filterrific-periodically-observed` class.

```erb
<%= form_for_filterrific @filterrific, html: { id: 'filterrific-no-ajax-auto-submit' } do |f| %>
...
  <%= f.submit 'Filter' %>
<% end %>
```

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