### Install Marten from Sources

Source: https://github.com/martenframework/marten/blob/main/docs/docs/getting-started/installation.md

Install Marten by cloning the repository, installing dependencies, and building the CLI from source.

```bash
git clone https://github.com/martenframework/marten
cd marten
shards install
crystal build src/marten_cli.cr -o bin/marten
mv bin/marten /usr/local/bin
```

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

### Marten Pagination Example

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/queries.md

Demonstrates how to use Marten's pagination mechanism to retrieve and iterate over records split across pages. Shows how to get paginator metadata and access individual pages.

```crystal
query_set = Article.filter(published: true)

paginator = query_set.paginator(10)
paginator.page_size   # => 10
paginator.pages_count # => 6
paginator.total_count # => 60

# Retrieve the first page and iterate over the underlying records
page = paginator.page(1)
page.each { |article| puts article }
page.number               # 1
page.previous_page?       # => false
page.previous_page_number # => nil
page.next_page?           # => true
page.next_page_number     # => 2
page.total_count          # => 60
```

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

### Start Local Development Server

Source: https://github.com/martenframework/marten/blob/main/docs/README.md

Starts a local development server for live preview. Changes are reflected without a server restart.

```bash
$ yarn start
```

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

### Install Crystal using APT

Source: https://github.com/martenframework/marten/blob/main/docs/docs/getting-started/installation.md

Install Crystal on Ubuntu, Debian, or other APT-based Linux distributions.

```bash
curl -fsSL https://crystal-lang.org/install.sh | sudo bash
```

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

### Example Output of 'marten help'

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/management-commands.md

An example of the output when running 'marten help', showing the usage pattern and a list of available commands.

```bash
Usage: marten [command] [options] [arguments]

Available commands:

[marten]

  › clearsessions    Clear all expired sessions.
  › collectassets    Collect all the assets and copy them in a unique storage.
  › gen / g          Generate various structures, abstractions, and values within an existing project.
  › genmigrations    Generate new database migrations.
  › listmigrations   List all database migrations.
  › migrate          Run database migrations.
  › new              Initialize a new Marten project or application repository.
  › play             Start a Crystal playground server initialized for the current project.
  › resetmigrations  Reset an existing set of migrations into a single one.
  › routes           Display all the routes of the application.
  › seed             Populate the database by running the seed file.
  › serve / s        Start a development server that is automatically recompiled when source files change.
  › version          Show the Marten version.

Run a command followed by --help to see command specific information, ex:
marten [command] --help
```

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

### Install Crystal

Source: https://github.com/martenframework/marten/blob/main/docs/docs/deployment/how-to/deploy-to-an-ubuntu-server.md

Installs Crystal on an Ubuntu server using the official installation script. Ensure you have sudo permissions.

```bash
curl -fsSL https://crystal-lang.org/install.sh | sudo bash
```

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

### Install Crystal and Shards using Pacman

Source: https://github.com/martenframework/marten/blob/main/docs/docs/getting-started/installation.md

Install Crystal and the 'shards' command-line tool on ArchLinux and its derivatives using Pacman.

```bash
sudo pacman -S crystal shards
```

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

### Marten Generator Help Output Example

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/generators.md

Provides an example of the output when listing available generators, including common generators and usage instructions.

```bash
Usage: marten gen [options] [generator]

Generate various structures, abstractions, and values within an existing project.

Arguments:
    generator                        Name of the generator to use

Options:
    --error-trace                    Show full error trace (if a compilation is involved)
    --no-color                       Disable colored output
    -h, --help                       Show this help

Available generators are listed below.

[marten]

  › app
  › auth
  › email
  › handler
  › model
  › schema
  › secretkey

Run a generator followed by --help to see generator specific information, ex:
marten gen [generator] --help
```

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

### Install Project Dependencies

Source: https://github.com/martenframework/marten/blob/main/docs/README.md

Installs project dependencies using Yarn. This is the first step before running any other commands.

```bash
$ yarn
```

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

### Start Marten Playground Server

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/reference/management-commands.md

Starts the Crystal playground server for the current project. Use --open to automatically open it in the default browser.

```bash
marten play

```

```bash
marten play --open

```

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

### Start Marten Development Server (Alias)

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/reference/management-commands.md

Starts the development server using the 's' alias. This is a shortcut for the 'marten serve' command.

```bash
marten s

```

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

### Start Marten Development Server

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/reference/management-commands.md

Starts a development server that recompiles automatically when source files change. Use --open to automatically open it in the default browser or specify a custom port.

```bash
marten serve

```

```bash
marten serve -p 3000

```

```bash
marten serve --open

```

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

### Start and Restart SystemD Service

Source: https://github.com/martenframework/marten/blob/main/docs/docs/deployment/how-to/deploy-to-an-ubuntu-server.md

Commands to start and restart the SystemD service for the application. Use 'start' for the initial launch and 'restart' for subsequent updates.

```bash
service <yourapp> start
```

```bash
service <yourapp> restart
```

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

### Install Crystal using Homebrew

Source: https://github.com/martenframework/marten/blob/main/docs/docs/getting-started/installation.md

Install Crystal on macOS or Linux using the Homebrew package manager.

```bash
brew install crystal
```

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

### Install Marten CLI using Homebrew

Source: https://github.com/martenframework/marten/blob/main/docs/docs/getting-started/installation.md

Install the Marten CLI tool on macOS or Linux using Homebrew.

```bash
brew tap martenframework/marten
brew trust martenframework/marten
brew install marten
```

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

### Install Required Packages

Source: https://github.com/martenframework/marten/blob/main/docs/docs/deployment/how-to/deploy-to-an-ubuntu-server.md

Installs essential packages like git, nginx, and postgresql on Ubuntu. These are needed for version control, serving the application, and database management.

```bash
sudo apt-get install git nginx postgresql
```

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

### Install Project Dependencies

Source: https://github.com/martenframework/marten/blob/main/docs/docs/deployment/how-to/deploy-to-an-ubuntu-server.md

Installs project dependencies using the 'shards' package manager. This command should be run from the project's root directory.

```bash
shards install
```

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

### Install Marten CLI using AUR

Source: https://github.com/martenframework/marten/blob/main/docs/docs/getting-started/installation.md

Install the Marten CLI using an AUR helper like 'yay' on ArchLinux and its derivatives.

```bash
yay -S marten
```

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

### Basic Marten Spec Example

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/testing.md

A simple example of a Marten spec file. Always ensure that './spec_helper' is required at the top of your spec files to set up the testing environment correctly.

```crystal
require "./spec_helper"

describe MySuperAbstraction do
  describe "#foo" do
    it "returns bar" do
      obj = MySuperAbstraction.new
      obj.foo.should eq "bar"
    end
  end
end
```

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

### List All Migrations for All Apps

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/reference/management-commands.md

Lists all available database migrations for all installed applications. This command helps in understanding the current migration status across the project.

```bash
marten listmigrations
```

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

### Basic Schema Migration Example

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/migrations.md

Defines a migration to add a new column and remove an old one from the `press_article` table.

```crystal
# Generated by Marten 0.1.0 on 2022-03-30 22:13:06 -04:00

class Migration::Press::V202203302213061 < Marten::Migration
  depends_on :press, "202203111822091_initial"

  def forward
    add_column :press_article, :rating, :int, null: true
    remove_column :press_article, :old_status
  end

  def backward
    # do something else
  end
end
```

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

### Displaying Generator Help Information

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/generators.md

Shows how to get specific help for a particular generator by appending the --help flag.

```bash
marten gen [generator] --help
```

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

### Render a template with context

Source: https://github.com/martenframework/marten/blob/main/docs/docs/templates/reference/tags.md

Example demonstrating how a template can include another and utilize variables from the parent context. The output depends on the `name` variable provided.

```html
Hello, {{ name }}! {% include "question.html" %}
```

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

### Example Asset Manifest JSON

Source: https://github.com/martenframework/marten/blob/main/docs/docs/assets/introduction.md

A sample JSON manifest file showing the mapping between original asset filenames and their fingerprinted counterparts.

```json
{
  "app/home.css": "app/home.9495841be78cdf06c45d.css",
  "app/home.js": "app/home.9495841be78cdf06c45d.js"
}
```

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

### Accept Arguments and Options in a Command

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/how-to/create-custom-commands.md

Use the `#setup` method to define arguments and options for your command. Arguments are positional, while options use flags like `--option` or `-o`.

```crystal
class MyCommand < Marten::CLI::Command
  help "Command that does something"

  @arg1 : String?
  @example : Bool = false

  def setup
    on_argument(:arg1, "The first argument") { |v| @arg1 = v }
    on_option("example", "An example option") { @example = true }
  end

  def run
    # Do something
  end
end
```

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

### RecordDelete Handler Usage

Source: https://github.com/martenframework/marten/blob/main/docs/versioned_docs/version-0.6/handlers-and-http/reference/generic-handlers.md

Example of how to use the RecordDelete handler to delete a specific model record. It can be used with POST requests for deletion or GET requests to display a confirmation page.

```APIDOC
## RecordDelete Handler

### Description
Handler allowing to delete a specific model record. This handler can be used to delete an existing model record by issuing a POST request. Optionally the handler can be accessed with a GET request and a template can be displayed in this case; this allows to display a confirmation page to users before deleting the record.

### Method
POST or GET

### Endpoint
(Not explicitly defined, depends on routing)

### Parameters
(Not explicitly defined, depends on model and routing)

### Request Example
```crystal
class ArticleDeleteHandler < Marten::Handlers::RecordDelete
  model Article
  template_name "articles/delete.html"
  success_route_name "article_delete_success"
end
```

### Response
#### Success Response (302 Found)
Redirects to the success route or URL.

#### Response Example
(Redirects to a specified route or URL)
```

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

### Complex Filters with AND and NOT using q Expressions

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/queries.md

Combine `q` expressions using AND (`&`) and NOT (`-`) operators to build intricate filter logic. This example finds articles starting with 'Top' but not authored by 'John'.

```crystal
Article.filter {
  (q(title__startswith: "Top") | q(title__startswith: "10")) & -q(author__first_name: "John")
}
```

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

### Complex Filters with OR using q Expressions

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/queries.md

Use the `q` method within filter blocks to combine conditions with logical OR. This example retrieves articles where the title starts with 'Top' or '10'.

```crystal
Article.filter { q(title__startswith: "Top") | q(title__startswith: "10") }
```

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

### Filtering Relations with Field Predicate Types

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/queries.md

Apply specific field predicate types (like `__startswith`) when filtering through relations. This example finds authors whose hometown name starts with 'New'.

```crystal
Author.filter(author__hometown__name__startswith: "New")
```

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

### Create Project Folders

Source: https://github.com/martenframework/marten/blob/main/docs/docs/deployment/how-to/deploy-to-an-ubuntu-server.md

Creates the directory structure for your application and sets ownership to the deployment user. Replace <yourapp> with your application's name.

```bash
sudo mkdir /srv/<yourapp>
sudo chown deploy:deploy /srv/<yourapp>
```

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

### ANDing Multiple Field Predicates within a q Expression

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/queries.md

When multiple field predicates are defined inside a single `q()` expression, they are combined using an implicit AND. This example filters for articles starting with 'Top' and authored by 'John Doe'.

```crystal
Article.filter {
  q(title__startswith: "Top") & -q(author__first_name: "John", author__last_name: "Doe")
}
```

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

### Start Marten Documentation Live Server

Source: https://github.com/martenframework/marten/blob/main/docs/docs/the-marten-project/contributing.md

Run the Docusaurus development server to preview documentation changes locally. Access the live server at http://localhost:3000/docs/.

```bash
npm run start
```

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

### Create New Project with Database Configuration

Source: https://github.com/martenframework/marten/blob/main/docs/versioned_docs/version-0.6/development/reference/management-commands.md

Creates a new project repository structure with a preconfigured PostgreSQL database.

```bash
marten new project myblog --database=postgresql
```

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

### Default Installed Apps Configuration

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/reference/settings.md

An empty array representing the default configuration for installed Marten applications.

```crystal
[] of Marten::Apps::Config.class

```

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

### Implement a Custom File System Storage

Source: https://github.com/martenframework/marten/blob/main/docs/docs/files/how-to/create-custom-file-storages.md

This example shows a custom file system storage implementation that reads and writes files to a specific folder on the local file system. It requires implementing methods for saving, deleting, opening, checking existence, retrieving size, and generating URLs for files.

```crystal
require "file_utils"

class FileSystem < Marten::Core::Storage::Base
  def initialize(@root : String, @base_url : String)
  end

  def delete(filepath : String) : Nil
    File.delete(path(filepath))
  rescue File::NotFoundError
    raise Marten::Core::Storage::Errors::FileNotFound.new("File '#{filepath}' cannot be found")
  end

  def exists?(filepath : String) : Bool
    File.exists?(path(filepath))
  end

  def open(filepath : String) : IO
    File.open(path(filepath), mode: "rb")
  rescue File::NotFoundError
    raise Marten::Core::Storage::Errors::FileNotFound.new("File '#{filepath}' cannot be found")
  end

  def size(filepath : String) : Int64
    File.size(path(filepath))
  end

  def url(filepath : String) : String
    File.join(base_url, URI.encode_path(filepath))
  end

  def write(filepath : String, content : IO) : Nil
    new_path = path(filepath)

    FileUtils.mkdir_p(Path[new_path].dirname)

    File.open(new_path, "wb") do |new_file|
      IO.copy(content, new_file)
    end
  end

  private getter root
  private getter base_url

  private def path(filepath)
    File.join(root, filepath)
  end
end
```

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

### Verify Marten CLI Installation

Source: https://github.com/martenframework/marten/blob/main/docs/docs/getting-started/installation.md

Check if the Marten CLI is installed and accessible by running the version command.

```bash
marten -v
```

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

### Configure PostgreSQL Database with Options

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/reference/settings.md

Demonstrates setting additional options for a PostgreSQL database, such as SSL mode.

```crystal
config.database do |db|
  db.backend = :postgresql
  db.host = "localhost"
  db.name = "my_db"
  db.user = "my_user"
  db.password = "my_password"
  db.options = {"sslmode" => "disable"}
end
```

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

### Deliver a Welcome Email

Source: https://github.com/martenframework/marten/blob/main/docs/docs/emailing/introduction.md

Initialize and deliver a WelcomeEmail instance synchronously. The configured emailing backend will handle the actual delivery.

```crystal
email = WelcomeEmail.new(user)
email.deliver
```

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

### Use Custom FileSystem Storage in Crystal

Source: https://github.com/martenframework/marten/blob/main/docs/docs/files/managing-files.md

Shows how to initialize and use a custom FileSystem storage with a specified root and base URL. This allows for flexible file management outside the default media storage.

```crystal
file = File.open("test.txt")
storage = Marten::Core::Storage::FileSystem.new(root: "/tmp", base_url: "/tmp")

filepath = storage.save("test.txt", file)
storage.exists?(filepath)  # => true
storage.exists?("unknown") # => false
storage.size(filepath)     # => 13
storage.url(filepath)      # => "/tmp/test.txt"
storage.delete(filepath)   # => nil
storage.exists?(filepath)  # => false
```

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

### Configure Installed Applications

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/applications.md

Specify the list of Marten applications to be installed in a project by adding their respective classes to the 'installed_apps' configuration setting.

```crystal
Marten.configure do |config|
  config.installed_apps = [
    FooApp,
    BarApp,
  ]
end
```

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

### Create New Marten Project with PostgreSQL Database

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/reference/management-commands.md

Initializes a new Marten project and preconfigures it with a PostgreSQL database.

```bash
marten new project myblog --database=postgresql
```

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

### Filter by string starting (case-sensitive)

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/reference/query-set.md

Use `startswith` to filter records where a field's value starts with a specific substring. This is case-sensitive.

```crystal
Article.all.filter(title__startswith: "Top")
```

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

### Initialize FileSystem Loader

Source: https://github.com/martenframework/marten/blob/main/docs/docs/templates/reference/loaders.md

Use this loader to retrieve templates directly from a specified directory on the file system. Provide the root template directory path during initialization.

```crystal
loader = Marten::Template::Loader::FileSystem.new("/path/to/templates")
```

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

### Deploy application to Fly.io

Source: https://github.com/martenframework/marten/blob/main/docs/docs/deployment/how-to/deploy-to-fly-io.md

Upload your application's code to Fly.io. This command builds a Docker image, pushes it to the registry, and launches a container.

```bash
fly deploy
```

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

### Install Marten Dependencies

Source: https://github.com/martenframework/marten/blob/main/docs/docs/the-marten-project/contributing.md

Install the necessary Crystal shards and Node.js dependencies for Marten development. This command also handles documentation dependencies.

```bash
make
```

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

### Generate New Application

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/generators.md

Creates a new Marten application named 'blogging'.

```bash
marten gen app blogging
```

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

### Configure Installed Apps

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/introduction.md

Configures Marten to include a custom application (`MyApp`) in the list of installed applications. This ensures models from this app are recognized.

```crystal
Marten.configure do |config|
  config.installed_apps = [
    MyApp,
    # other apps...
  ]
end
```

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

### Implement an In-Memory Cache Store

Source: https://github.com/martenframework/marten/blob/main/docs/docs/caching/how-to/create-custom-cache-stores.md

This example demonstrates how to create a custom in-memory cache store by inheriting from `Marten::Cache::Store::Base` and implementing the necessary methods to manage cache entries in a hash.

```crystal
class MemoryStore < Marten::Cache::Store::Base
  @data = {} of String => String

  def initialize(
    @namespace : String? = nil,
    @expires_in : Time::Span? = nil,
    @version : Int32? = nil,
    @compress = false,
    @compress_threshold = DEFAULT_COMPRESS_THRESHOLD
  )
    super
  end

  def clear : Nil
    @data.clear
  end

  def decrement(
    key : String,
    amount : Int32 = 1,
    expires_at : Time? = nil,
    expires_in : Time::Span? = nil,
    version : Int32? = nil,
    race_condition_ttl : Time::Span? = nil,
    compress : Bool? = nil,
    compress_threshold : Int32? = nil
  )
    apply_increment(
      key,
      amount: -amount,
      expires_at: expires_at,
      expires_in: expires_in,
      version: version,
      race_condition_ttl: race_condition_ttl,
      compress: compress,
      compress_threshold: compress_threshold
    )
  end

  def increment(
    key : String,
    amount : Int32 = 1,
    expires_at : Time? = nil,
    expires_in : Time::Span? = nil,
    version : Int32? = nil,
    race_condition_ttl : Time::Span? = nil,
    compress : Bool? = nil,
    compress_threshold : Int32? = nil
  ) : Int
    apply_increment(
      key,
      amount: amount,
      expires_at: expires_at,
      expires_in: expires_in,
      version: version,
      race_condition_ttl: race_condition_ttl,
      compress: compress,
      compress_threshold: compress_threshold
    )
  end

  private getter data

  private def apply_increment(
    key : String,
    amount : Int32 = 1,
    expires_at : Time? = nil,
    expires_in : Time::Span? = nil,
    version : Int32? = nil,
    race_condition_ttl : Time::Span? = nil,
    compress : Bool? = nil,
    compress_threshold : Int32? = nil
  )
    normalized_key = normalize_key(key.to_s)
    entry = deserialize_entry(read_entry(normalized_key))

    if entry.nil? || entry.expired? || entry.mismatched?(version || self.version)
      write(
        key: key,
        value: amount.to_s,
        expires_at: expires_at,
        expires_in: expires_in,
        version: version,
        race_condition_ttl: race_condition_ttl,
        compress: compress,
        compress_threshold: compress_threshold
      )
      amount
    else
      new_amount = entry.value.to_i + amount
      entry = Entry.new(new_amount.to_s, expires_at: entry.expires_at, version: entry.version)
      write_entry(normalized_key, serialize_entry(entry))
      new_amount
    end
  end

  private def delete_entry(key : String) : Bool
    deleted_entry = @data.delete(key)
    !!deleted_entry
  end

  private def read_entry(key : String) : String?
    data[key]?
  end

  private def write_entry(
    key : String,
    value : String,
    expires_in : Time::Span? = nil,
    race_condition_ttl : Time::Span? = nil
  )
    data[key] = value
    true
  end
end
```

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

### Filter by string starting (case-insensitive)

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/reference/query-set.md

Use `istartswith` to filter records where a field's value starts with a specific substring, ignoring case.

```crystal
Article.all.filter(title__istartswith: "top")
```

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

### Initialize and Setup Marten Project in Playground

Source: https://github.com/martenframework/marten/blob/main/docs/docs/getting-started/tutorial.md

Boilerplate code for the Marten playground. It requires project dependencies and sets up Marten. Subsequent code snippets should be added below this.

```crystal
require "./src/project"

# Setup the project.
Marten.setup

# Write your code here.
```

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

### Fly.io Application Configuration

Source: https://github.com/martenframework/marten/blob/main/docs/docs/deployment/how-to/deploy-to-fly-io.md

Example `fly.toml` file content generated by `fly launch`. It defines the app name, primary region, environment variables, and service settings.

```toml
app = "<yourapp>"
primary_region = "<yourregion>"

[env]
  MARTEN_ALLOWED_HOSTS = "<yourapp>.fly.dev"

[http_service]
  internal_port = 8000
  force_https = true
  auto_stop_machines = true
  auto_start_machines = true
```

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

### Create New Marten Application

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/reference/management-commands.md

Initializes a new Marten application repository structure with the specified name.

```bash
marten new app auth
```

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

### Listing Available Generators

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/generators.md

Demonstrates how to list all generators available within the current Marten project.

```bash
marten gen
```

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

### Fetch Single Record with `get!`

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/raw-sql.md

Use the `get!` method with raw SQL predicates to retrieve a single record. Raises an exception if no record is found.

```crystal
article = Article.get!("title = :title AND created_at > :created_at", title: "Hello World!", created_at: "2022-10-30")
```

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

### Fetch Single Record with `get`

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/raw-sql.md

Use the `get` method with raw SQL predicates to retrieve a single record. Returns `nil` if no record matches.

```crystal
article = Article.get("title = ? AND created_at > ?", "Hello World!", "2022-10-30")
```

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

### Article Spec Example with Nested Helper

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/testing.md

An example spec file for an Article model, utilizing a nested spec_helper.cr for its directory. This demonstrates how to structure specs within organized folders.

```crystal
require "./spec_helper"

describe Article do
  # ...
end
```

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

### Create New Marten Project

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/reference/management-commands.md

Initializes a new Marten project repository structure with the specified name.

```bash
marten new project myblog
```

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

### Apply Database Migrations

Source: https://github.com/martenframework/marten/blob/main/docs/docs/deployment/introduction.md

Run this command to create or update database tables based on your project's models. Ensure you have compiled the `manage` binary.

```bash
bin/manage migrate
```

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

### Simulate GET Request and Verify Response

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/testing.md

Use the test client to perform a GET request and assert the status code and Location header of the response. This is useful for testing redirects.

```crystal
describe MyRedirectHandler do
  describe "#get" do
    it "returns the expected redirect response" do
      response = Marten::Spec.client.get("/my-redirect-handler", query_params: {"foo" => "bar"})

      response.status.should eq 302
      response.headers["Location"].should eq "/redirected"
    end
  end
end
```

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

### Define a Basic Management Command

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/how-to/create-custom-commands.md

Subclass Marten::CLI::Command and define a `#run` method to implement command logic. Use the `#help` class method to set the command's help text.

```crystal
class MyCommand < Marten::CLI::Command
  help "Command that does something"

  def run
    # Do something
  end
end
```

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

### Run the Marten Server

Source: https://github.com/martenframework/marten/blob/main/docs/docs/deployment/introduction.md

Start the Marten development server. It's recommended to run this behind a reverse proxy like Nginx in production, and avoid using HTTP port 80.

```bash
bin/server
```

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

### Retrieve a Specific Record by ID or Field

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/queries.md

Use the `#get` method to retrieve a single record by its primary key or other fields. Returns `nil` if not found. Use `#get!` to raise an error if not found.

```crystal
Author.get(id: 1)
Author.get(first_name: "John")
```

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

### Resolve URL and Simulate GET Request

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/testing.md

Demonstrates how to dynamically resolve a handler URL using Marten's routing before making a GET request with the test client. This avoids hardcoding paths.

```crystal
url = Marten.routes.reverse("article_detail", pk: 42)
response = Marten::Spec.client.get(url, query_params: {"foo" => "bar"})
```

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

### Retrieve a single model instance with `get!`

Source: https://github.com/martenframework/marten/blob/main/docs/versioned_docs/version-0.6/models-and-databases/reference/query-set.md

Use `get!` to retrieve a single record, raising `RecordNotFound` if no record is found or `MultipleRecordsFound` if more than one record matches. This method is useful when you expect a record to exist.

```crystal
query_set = Post.all
post_1 = query_set.get!(id: 123)
post_2 = query_set.get!(id: 456, is_published: false)
```

```crystal
query_set = Post.all
post_1 = query_set.get! { q(id: 123) }
post_2 = query_set.get! { q(id: 456, is_published: false) }
```

```crystal
Author.get!("id=?", 42)
Author.get!("id=:id", id: 42)
```

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

### Create and Set Permissions for settings.env

Source: https://github.com/martenframework/marten/blob/main/docs/docs/deployment/how-to/deploy-to-an-ubuntu-server.md

Create an empty settings.env file and set its permissions. This file is used to store environment-specific settings.

```bash
touch /srv/<yourapp>/settings.env
chmod 600 /srv/<yourapp>/settings.env
```

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

### Retrieve a single model instance with `get`

Source: https://github.com/martenframework/marten/blob/main/docs/versioned_docs/version-0.6/models-and-databases/reference/query-set.md

Use `get` to retrieve a single record by its primary key or a unique field. It returns `nil` if no record is found and raises `MultipleRecordsFound` if more than one record matches.

```crystal
query_set = Post.all
post_1 = query_set.get(id: 123)
post_2 = query_set.get(id: 456, is_published: false)
```

```crystal
query_set = Post.all
post_1 = query_set.get { q(id: 123) }
post_2 = query_set.get { q(id: 456, is_published: false) }
```

```crystal
Author.get("id=?", 42)
Author.get("id=:id", id: 42)
```

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

### Example Template for Article Detail

Source: https://github.com/martenframework/marten/blob/main/docs/docs/handlers-and-http/generic-handlers.md

An example HTML template that displays details of an Article record fetched by the RecordDetail handler. It accesses the record's attributes like title and created_at from the 'record' context variable.

```html
<ul>
  <li>Title: {{ record.title }}</li>
  <li>Created at: {{ record.created_at }}</li>
</ul>
```

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

### Generated Migration File Example

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/migrations.md

A sample migration file generated by Marten, detailing the addition of a 'hometown' column to the 'blog_author' table. It specifies dependencies and the migration plan.

```crystal
# Generated by Marten 0.1.0 on 2022-06-22 18:56:24 -04:00

class Migration::Blog::V202206221856241 < Marten::Migration
  depends_on :blog, "202205290942181_previous_migration_name"

  def plan
    add_column :blog_author, :hometown, :string, max_size: 255, null: true
  end
end
```

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

### Apply All Migrations

Source: https://github.com/martenframework/marten/blob/main/docs/docs/development/reference/management-commands.md

Applies all pending migrations for all installed applications. This is the default behavior when no arguments are provided.

```bash
marten migrate                     # Applies all the non-applied migrations for all the installed apps
```

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

### Example HTML for List Inclusion Tag

Source: https://github.com/martenframework/marten/blob/main/docs/docs/templates/how-to/create-custom-tags.md

This HTML template is rendered by the `ListTag` to display list items.

```html
<ul>
  {% for item in list %}
    <li>{{ item }}</li>
  {% endfor %}
</ul>
```

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

### Generate New Project with Authentication

Source: https://github.com/martenframework/marten/blob/main/docs/docs/authentication/introduction.md

Use the `--with-auth` option with the `marten new` command to generate a new project that includes the authentication application.

```bash
marten new project myblog --with-auth
```

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

### Create New Project Without Database Configuration

Source: https://github.com/martenframework/marten/blob/main/docs/versioned_docs/version-0.6/development/reference/management-commands.md

Creates a new project repository structure without any preconfigured database.

```bash
marten new project myblog --database=none
```

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

### Customizing QuerySet for Record Update

Source: https://github.com/martenframework/marten/blob/main/docs/docs/handlers-and-http/reference/generic-handlers.md

Customize the queryset to filter records before updating, for example, by associating them with the current user.

```crystal
class ArticleUpdateHandler < Marten::Handlers::RecordUpdate
  queryset Article.filter(user: request.user)
  schema ArticleUpdateSchema
  template_name "articles/update.html"
  success_route_name "my_form_success"
end
```

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

### Get Primary Key Values

Source: https://github.com/martenframework/marten/blob/main/docs/docs/models-and-databases/reference/query-set.md

Retrieves an array of primary key values for all records targeted by the query set.

```crystal
Post.all.pks # => [1, 2, 3]
```

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

### Including Partial Templates

Source: https://github.com/martenframework/marten/blob/main/docs/docs/templates/introduction.md

Demonstrates how to include partial templates with and without additional context variables.

```html
{% include "partials/button.html" with type="primary" %}
{% include "partials/button.html" with type="primary", text="Custom text" %}
```

```html
{% include "partials/other_snippet.html" %}
```