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- 7.1.3.4
- What's this?
Responder is 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.find(: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 #to_xml on the given resource; 3) if the responder does not respond_to :to_xml, call #to_format 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 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.comments.build(params[:task]) flash[:notice] = 'Task was successfully created.' if @task.save respond_with(@project, @task) end
Giving an array of resources, you ensure 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)
Check polymorphic_url documentation for more examples.
Constants
ACTIONS_FOR_VERBS = { :post => :new, :put => :edit }
Attributes
[R] | controller | |
[R] | request | |
[R] | format | |
[R] | resource | |
[R] | resources | |
[R] | options |