A Crystal router
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README.adoc

Orion

Purpose

The purpose of the Orion router is to connect URLs to code. It provides a flexible and comprehensive DSL that will allow you to cover a variety of use cases. In addition, Orion will also generate a series of helpers to easily reference the defined paths within your application.

Installation

Add this to your application’s shard.yml:

dependencies:
  orion:
    github: obsidian/orion
  1. and require Orion in your project.

require "orion"

Usage

Defining a router

You can define a router by using the router macro with a constant name.

router MyApplicationRouter do
  # ...
end

Generic route arguments

There are a variety of ways that you can interact with basic routes. Below are some examples and guidelines on the different ways you can interact with the router.

Using to: String to target a controller and action

One of the most common ways we will be creating routes in this guide is to use the to argument supplied with a controller and action in the form of a string. In the example below UsersController#create will map to UsersController.new(cxt : HTTP::Server::Context).create.

router MyApplicationRouter do
  post "users", to: "UsersController#create"
end
Non-constant

By passing a lowercased string, it still camelcase the string and add Controller. In the example below users#create will map to UsersController.new(cxt : HTTP::Server::Context).create.

router MyApplicationRouter do
  post "users", to: "users#create"
end

Using controller: Type and action: Method

A longer form of the to argument strategy above allows us to pass the controller and action independently.

router MyApplicationRouter do
  post "users", controller: UsersController, action: create
end

Using block syntax

Sometimes, we may want a more kemal or sinatra like approach. To accomplish this, we can simply pass a block that yields HTTP::Server::Context.

router MyApplicationRouter do
  post "users" do |context|
    context.response.puts "foo"
  end
end

Using a call able object

Lastly a second argument can be any object that responds to #call(cxt : HTTP::Server::Context).

router MyApplicationRouter do
  post "users", ->(context : HTTP::Server::Context) {
    context.response.puts "foo"
  }
end

Basic Routing

Base route using root

Lets define the routers’s root route. root is simply an alias for get '/', action. All routes can either be a String pointing to a Controller action or a Proc accepting HTTP::Server::Context as a single argument. If a String is used like controller#action, it will expand into Controller.new(context : HTTP::Server::Context).action, therefor A controller must have an initializer that takes HTTP::Server::Context as an argument, and the specified action must not contain arguments.

  router MyApplicationRouter do
    root to: "home#index"
  end

HTTP verb based routes

A common way to interact with the router is to use standard HTTP verbs. Orion supports all the standard HTTP verbs:

get, head, post, put, delete, connect, options, trace, and patch

You can simply use one of the methods within the router and pass it’s router and any variation of the Generic Route Arguments.

router MyApplicationRouter do
  post "users", to: "users#create"
end

Catch all routes using match

In some instances you may just want to redirect all verbs to a particular controller and action.

You can simply use the match method within the router and pass it’s router and any variation of the Generic Route Arguments.

router MyApplicationRouter do
  match "404", controller: ErrorsController, action: error_404
end

Resource Based Routing

A common way in Orion to route is to do so against a known resource. This method will create a series of routes targeted at a specific controller.

The following is an example controller definition and the matching resources definition.

class PostsController
  include Orion::ControllerHelper
  include ResponseHelpers

  def index
    @posts = Post.all
    render :index
  end

  def new
    @post = Post.new
    render :new
  end

  def create
    post = Post.create(request)
    redirect to: post_path post_id: post.id
  end

  def show
    @post = Post.find(request.path_params["post_id"])
  end

  def edit
    @post = Post.find(request.path_params["post_id"])
    render :edit
  end

  def update
    post = Post.find(request.path_params["post_id"])
    HTTP::FormData.parse(request) do |part|
      post.attributes[part.name] = part.body.gets_to_end
    end
    redirect to: post_path post_id: post.id
  end

  def delete
    post = Post.find(request.path_params["post_id"])
    post.delete
    redirect to: posts_path
  end

end

router MyApplication do
  resources :posts
end

Including/Excluding Actions

By default, the actions index, new, create, show, edit, update, delete are included. You may include or exclude explicitly by using the only and except params.

NOTE: The index action is not added for singular resources.
router MyApplication do
  resources :posts, except: [:edit, :update]
  resources :users, only: [:new, :create, :show]
end

Nested Resources and Routes

You can add nested resources and member routes by providing a block to the resources definition.

router MyApplication do
  resources :posts do
    post "feature", action: feature
    resources :likes
    resources :comments
  end
end

Singular Resources

In addition to using the collection of resources method, You can also add singular resources which do not provide a id_param or index action.

router MyApplication do
  resource :profile
end

Customizing ID

You can customize the ID path parameter by passing the id_param parameter.

router MyApplication do
  resources :posts, id_param: :article_id
end

Constraining the ID

You can set constraints on the ID parameter by passing the id_constraint parameter.

see param constraints for more details

router MyApplication do
  resources :posts, id_constraint: /^\d{4}$/
end

Constraints

Similar to basic routes, resource and resources support the format, accept, content_type, and type constraints.

Instrumenting handlers (a.k.a. middleware)

Instances or Classes implementing HTTP::Handler (a.k.a. middleware) can be inserted directly in your routes by using the use method.

Handlers will only apply to the routes specified below them, so be sure to place your handlers near the top of your route.
router MyApplicationRouter do
  use HTTP::ErrorHandler
  use HTTP::LogHandler.new(File.open("tmp/application.log"))
end

Nested Routes using scope

Scopes are a method in which you can nest routes under a common path. This prevents the need for duplicating paths and allows a developer to easily change the parent of a set of child paths.

router MyApplicationRouter do
  scope "users" do
    root to: "Users#index"
    get ":id", to: "Users#show"
    delete ":id", to: "Users#destroy"
  end
end

Handlers within nested routes

Instances of HTTP::Handler can be used within a scope and will only apply to the subsequent routes within that scope. It is important to note that the parent context’s handlers will also be used.

Handlers will only apply to the routes specified below them, so be sure to place your handlers near the top of your scope.
router MyApplicationRouter do
  scope "users" do
    use AuthorizationHandler.new
    root to: "Users#index"
    get ":id", to: "Users#show"
    delete ":id", to: "Users#destroy"
  end
end

Route Helper prefixes

When using Helpers, you may want a prefix to be appended so that you don’t have to repeat it within each individual route. For example a scope with helper_prefix: "users" containing a route with helper: "show" will generate a helper method of users_show.

router MyApplicationRouter do
  scope "users", helper_prefix: "users" do
    use AuthorizationHandler.new
    get ":id", to: "Users#show", helper: "show"
  end
end
Caveats

When considering helpers within scopes you may want to use a longer form of the helper to get a better name. You can pass a named tuple with the fields name, prefix, and/or suffix.

router MyApplicationRouter do
  scope "users", helper_prefix: "user" do
    use AuthorizationHandler.new
    get ":id", to: "Users#show", helper: { prefix: "show" }
  end
end

The above example will expand into show_user instead of user_show.

Concerns – Reusable code in your routers

In some instances you may want to create a pattern or concern that you wish to repeat across scopes or resources in your router.

Defining a concern

To define a concern call concern with a Symbol for the name.

router MyApplicationRouter do
  concern :authenticated do
    use Authentication.new
  end
end

Using concerns

Once a concern is defined you can call implements with a named concern from anywhere in your router.

router MyApplicationRouter do
  concern :authenticated do
    use Authentication.new
  end

  scope "users" do
    implements :authenticated
    get ":id"
  end
end

Method Overrides

In some situations certain environments may not support certain HTTP methods, when in these environments, there are a few methods to force a different method in the router. In either of the methods below, if you intend to pass a body, you should be using the POST http method when you make the request.

Header Overrides

If your client has the ability to set headers you can use the built in ability to pass the X-HTTP-Method-Override: [METHOD] method with the method you wish to invoke on the router.

Parameter & Form Overrides

If your client has the ability to set headers you can use the Orion::Handlers::MethodOverrideParam to pass a _method=[METHOD] parameter as a query parameter or form field with the method you wish to invoke on the router.

router MyRouter do
  use Orion::Handlers::MethodOverrideParam.new
  # ... routes
end

Constraints - More advanced rules for your routes

Constraints can be used to further determine if a route is hit beyond just it’s path. Routes have some predefined constraints you can specify, but you can also pass in a custom constraint.

Parameter constraints

When defining a route, you can pass in parameter constraints. The path params will be checked against the provided regex before the route is chosen as a valid route.

router MyApplicationRouter do
  get "users/:id", constraints: { id: /[0-9]{4}/ }
end

Format constraints

You can constrain the request to a certain format. Such as restricting the extension of the URL to '.json'.

router MyApplicationRouter do
  get "api/users/:id", format: "json"
end

Request Mime-Type constraints

You can constrain the request to a certain mime-type by using the content_type param on the route. This will ensure that if the request has a body, that it provides the proper content type.

router MyApplicationRouter do
  put "api/users/:id", content_type: "application/json"
end

Response Mime-Type constraints

You can constrain the response to a certain mime-type by using the accept param on the route. This is similar to the format constraint, but allows clients to specify the Accept header rather than the extension.

Orion will automatically add mime-type headers for requests with no Accept header and a specified extension.
router MyApplicationRouter do
  get "api/users/:id", accept: "application/json"
end

Combined Mime-Type constraints

You can constrain the request and response to a certain mime-type by using the type param on the route. This will ensure that if the request has a body, that it provides the proper content type. In addition it will also validate that the client provides a proper accept header for the response.

Orion will automatically add mime-type headers for requests with no Accept header and a specified extension.
router MyApplicationRouter do
  put "api/users/:id", type: "application/json"
end

Host constraints

You can constrain the request to a specific host by wrapping routes in a host block. In this method, any routes within the block will be matched at that constraint.

You may also choose to limit the request to a certain format. Such as restricting the extension of the URL to '.json'.

router MyApplicationRouter do
  host "example.com" do
    get "users/:id", format: "json"
  end
end

Subdomain constraints

You can constrain the request to a specific subdomain by wrapping routes in a subdomain block. In this method, any routes within the block will be matched at that constraint.

You may also choose to limit the request to a certain format. Such as restricting the extension of the URL to '.json'.

router MyApplicationRouter do
  subdomain "api" do
    get "users/:id", format: "json"
  end
end

Custom Constraints

You can also pass in your own constraints by just passing a class/struct that implements the Orion::Constraint module.

struct MyConstraint
  def matches?(req : HTTP::Request)
    true
  end
end

router MyApplicationRouter do
  constraint MyConstraint.new do
    get "users/:id", format: "json"
  end
end

Route Helpers

Route helpers provide type-safe methods to generate paths and urls to defined routes in your application. By including the Helpers module on the router (i.e. MyApplicationRouter::Helpers) you can access any helper defined in the router by {{name}}_path to get its corresponding route. In addition, when you have a @context : HTTP::Server::Context instance var, you will also be able to access a {{name}}_url to get the full url.

router MyApplicationRouter do
  scope "users", helper_prefix: "user" do
    get "/new", to: "UsersController#new", helper: "new"
  end
end

class UsersController
  def new
  end
end

class MyController
  include MyApplicationRouter::Helpers
  delegate request, response, to: @context

  def initialize(@context : HTTP::Server::Context)
  end

  def new
    File.open("new.html") { |f| IO.copy(f, response) }
  end

  def show
    user = User.find(request.path_params["id"])
    response.headers["Location"] = new_user_path
    response.status_code = 301
    response.close
  end
end

Making route helpers from your routes

In order to make a helper from your route you can use the helper named argument in your route.

router MyApplicationRouter do
  scope "users" do
    get "/new", to: "Users#new", helper: "new"
  end
end

Using route helpers in your code

As you add helpers they are added to the nested Helpers module of your router. you may include this module anywhere in your code to get access to the methods, or call them on the module directly.

If @context : HTTP::Server::Context is present in the class, you will also be able to use the {helper}_url versions of the helpers.

router MyApplicationRouter do
  resources :users
end

class User
  include MyApplicationRouter::Helpers

  def route
    user_path user_id: self.id
  end
end

puts MyApplicationRouter::Helpers.users_path

Contributing

  1. Fork it https://github.com/<your-github-name>/orion/fork

  2. Create your feature branch (git checkout -b my-new-feature)

  3. Commit your changes (git commit -am 'Add some feature')

  4. Push to the branch (git push origin my-new-feature)

  5. Create a new Pull Request

Contributors