Class: ActionController::Responder

Inherits:
Object
  • Object
show all
Defined in:
actionpack/lib/action_controller/metal/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.

Builtin 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.



129
130
131
132
133
134
135
136
137
138
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 129

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)
end

Instance Attribute Details

#controller ⇒ Object (readonly)

Returns the value of attribute controller



121
122
123
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 121

def controller
  @controller
end

#format ⇒ Object (readonly)

Returns the value of attribute format



121
122
123
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 121

def format
  @format
end

#options ⇒ Object (readonly)

Returns the value of attribute options



121
122
123
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 121

def options
  @options
end

#request ⇒ Object (readonly)

Returns the value of attribute request



121
122
123
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 121

def request
  @request
end

#resource ⇒ Object (readonly)

Returns the value of attribute resource



121
122
123
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 121

def resource
  @resource
end

#resources ⇒ Object (readonly)

Returns the value of attribute resources



121
122
123
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 121

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.



150
151
152
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 150

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.



156
157
158
159
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 156

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.



179
180
181
182
183
184
185
186
187
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 179

def to_format
  if get? || !has_errors? || response_overridden?
    default_render
  else
    display_errors
  end
rescue ActionView::MissingTemplate => e
  api_behavior(e)
end

#to_html ⇒ Object

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



164
165
166
167
168
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 164

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.



171
172
173
 
# File 'actionpack/lib/action_controller/metal/responder.rb', line 171

def to_js
  default_render
end