Class: ActionController::Responder

Inherits:
Object
  • Object
show all
Defined in:
lib/action_controller/responder.rb

Overview

Responsible for exposing a resource to different mime requests, usually depending on the HTTP verb. The responder is triggered when respond_with is called. The simplest case to study is a GET request:

class PeopleController < ApplicationController
  respond_to :html, :xml, :json

  def index
    @people = Person.all
    respond_with(@people)
  end
end

When a request comes in, for example for an XML response, three steps happen:

1) the responder searches for a template at people/index.xml;

2) if the template is not available, it will invoke <code>#to_xml</code> on the given resource;

3) if the responder does not <code>respond_to :to_xml</code>, call <code>#to_format</code> on it.

Built-in HTTP verb semantics

The default Rails responder holds semantics for each HTTP verb. Depending on the content type, verb and the resource status, it will behave differently.

Using Rails default responder, a POST request for creating an object could be written as:

def create
  @user = User.new(params[:user])
  flash[:notice] = 'User was successfully created.' if @user.save
  respond_with(@user)
end

Which is exactly the same as:

def create
  @user = User.new(params[:user])

  respond_to do |format|
    if @user.save
      flash[:notice] = 'User was successfully created.'
      format.html { redirect_to(@user) }
      format.xml { render xml: @user, status: :created, location: @user }
    else
      format.html { render action: "new" }
      format.xml { render xml: @user.errors, status: :unprocessable_entity }
    end
  end
end

The same happens for PATCH/PUT and DELETE requests.

Nested resources

You can supply nested resources as you do in form_for and polymorphic_url. Consider the project has many tasks example. The create action for TasksController would be like:

def create
  @project = Project.find(params[:project_id])
  @task = @project.tasks.build(params[:task])
  flash[:notice] = 'Task was successfully created.' if @task.save
  respond_with(@project, @task)
end

Giving several resources ensures that the responder will redirect to project_task_url instead of task_url.

Namespaced and singleton resources require a symbol to be given, as in polymorphic urls. If a project has one manager which has many tasks, it should be invoked as:

respond_with(@project, :manager, @task)

Note that if you give an array, it will be treated as a collection, so the following is not equivalent:

respond_with [@project, :manager, @task]

Custom options

respond_with also allows you to pass options that are forwarded to the underlying render call. Those options are only applied for success scenarios. For instance, you can do the following in the create method above:

def create
  @project = Project.find(params[:project_id])
  @task = @project.tasks.build(params[:task])
  flash[:notice] = 'Task was successfully created.' if @task.save
  respond_with(@project, @task, status: 201)
end

This will return status 201 if the task was saved successfully. If not, it will simply ignore the given options and return status 422 and the resource errors. You can also override the location to redirect to:

respond_with(@project, location: root_path)

To customize the failure scenario, you can pass a block to respond_with:

def create
  @project = Project.find(params[:project_id])
  @task = @project.tasks.build(params[:task])
  respond_with(@project, @task, status: 201) do |format|
    if @task.save
      flash[:notice] = 'Task was successfully created.'
    else
      format.html { render "some_special_template" }
    end
  end
end

Using respond_with with a block follows the same syntax as respond_to.

Constant Summary collapse

DEFAULT_ACTIONS_FOR_VERBS = 
{
  post: :new,
  patch: :edit,
  put: :edit
}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(controller, resources, options = {}) ⇒ Responder

Returns a new instance of Responder.



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# File 'lib/action_controller/responder.rb', line 131

def initialize(controller, resources, options = {})
  @controller = controller
  @request = @controller.request
  @format = @controller.formats.first
  @resource = resources.last
  @resources = resources
  @options = options
  @action = options.delete(:action)
  @default_response = options.delete(:default_response)

  if options[:location].respond_to?(:call)
    location = options.delete(:location)
    options[:location] = location.call unless has_errors?
  end
end

Instance Attribute Details

#controller ⇒ Object (readonly)

Returns the value of attribute controller.



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# File 'lib/action_controller/responder.rb', line 123

def controller
  @controller
end

#format ⇒ Object (readonly)

Returns the value of attribute format.



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# File 'lib/action_controller/responder.rb', line 123

def format
  @format
end

#options ⇒ Object (readonly)

Returns the value of attribute options.



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# File 'lib/action_controller/responder.rb', line 123

def options
  @options
end

#request ⇒ Object (readonly)

Returns the value of attribute request.



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# File 'lib/action_controller/responder.rb', line 123

def request
  @request
end

#resource ⇒ Object (readonly)

Returns the value of attribute resource.



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# File 'lib/action_controller/responder.rb', line 123

def resource
  @resource
end

#resources ⇒ Object (readonly)

Returns the value of attribute resources.



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# File 'lib/action_controller/responder.rb', line 123

def resources
  @resources
end

Class Method Details

.call(*args) ⇒ Object

Initializes a new responder and invokes the proper format. If the format is not defined, call to_format.



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# File 'lib/action_controller/responder.rb', line 157

def self.call(*args)
  new(*args).respond
end

Instance Method Details

#respond ⇒ Object

Main entry point for responder responsible to dispatch to the proper format.



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# File 'lib/action_controller/responder.rb', line 163

def respond
  method = "to_#{format}"
  respond_to?(method) ? send(method) : to_format
end

#to_format ⇒ Object

All other formats follow the procedure below. First we try to render a template, if the template is not available, we verify if the resource responds to :to_format and display it.



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# File 'lib/action_controller/responder.rb', line 186

def to_format
  if !get? && has_errors? && !response_overridden?
    display_errors
  elsif has_view_rendering? || response_overridden?
    default_render
  else
    api_behavior
  end
rescue ActionView::MissingTemplate
  api_behavior
end

#to_html ⇒ Object

HTML format does not render the resource, it always attempt to render a template.



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# File 'lib/action_controller/responder.rb', line 171

def to_html
  default_render
rescue ActionView::MissingTemplate => e
  navigation_behavior(e)
end

#to_js ⇒ Object

to_js simply tries to render a template. If no template is found, raises the error.



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# File 'lib/action_controller/responder.rb', line 178

def to_js
  default_render
end