For a given controller action, #respond_with generates an appropriate response based on the mime-type requested by the client.
If the method is called with just a resource, as in this example -
class PeopleController < ApplicationController respond_to :html, :xml, :json def index @people = Person.all respond_with @people end end
then the mime-type of the response is typically selected based on the
request's Accept header and the set of available formats declared by
previous calls to the controller's class method
respond_to
. Alternatively the mime-type can be selected by
explicitly setting request.format
in the controller.
If an acceptable format is not identified, the application returns a
'406 - not acceptable' status. Otherwise, the default response is
to render a template named after the current action and the selected
format, e.g. index.html.erb
. If no template is available, the
behavior depends on the selected format:
-
for an html response - if the request method is
get
, an exception is raised but for other requests such aspost
the response depends on whether the resource has any validation errors (i.e. assuming that an attempt has been made to save the resource, e.g. by acreate
action) --
If there are no errors, i.e. the resource was saved successfully, the response
redirect
's to the resource i.e. itsshow
action. -
If there are validation errors, the response renders a default action, which is
:new
for apost
request or:edit
forpatch
orput
.
Thus an example like this -
respond_to :html, :xml def create @user = User.new(params[:user]) flash[:notice] = 'User was successfully created.' if @user.save respond_with(@user) end
is equivalent, in the absence of
create.html.erb
, to -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 } else format.html { render action: "new" } format.xml { render xml: @user } end end end
-
-
for a javascript request - if the template isn't found, an exception is raised.
-
for other requests - i.e. data formats such as xml, json, csv etc, if the resource passed to
respond_with
responds toto_<format>
, the method attempts to render the resource in the requested format directly, e.g. for an xml request, the response is equivalent to callingrender xml: resource
.
Nested resources
As outlined above, the resources
argument passed to
respond_with
can play two roles. It can be used to generate
the redirect url for successful html requests (e.g. for create
actions when no template exists), while for formats other than html and
javascript it is the object that gets rendered, by being converted directly
to the required format (again assuming no template exists).
For redirecting successful html requests, respond_with
also
supports the use of nested resources, which are supplied in the same way as
in form_for
and polymorphic_url
. For example -
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
This would cause respond_with
to redirect to
project_task_url
instead of task_url
. For request
formats other than html or javascript, if multiple resources are passed in
this way, it is the last one specified that is rendered.
Customizing response behavior
Like respond_to
, respond_with
may also be called
with a block that can be used to overwrite any of the default responses,
e.g. -
def create @user = User.new(params[:user]) flash[:notice] = "User was successfully created." if @user.save respond_with(@user) do |format| format.html { render } end end
The argument passed to the block is an ActionController::MimeResponds::Collector
object which stores the responses for the formats defined within the block.
Note that formats with responses defined explicitly in this way do not have
to first be declared using the class method respond_to
.
Also, a hash passed to respond_with
immediately after the
specified resource(s) is interpreted as a set of options relevant to all
formats. Any option accepted by render
can be used, e.g.
respond_with @people, status: 200
However, note that these options are ignored after an unsuccessful attempt
to save a resource, e.g. when automatically rendering :new
after a post request.
Two additional options are relevant specifically to
respond_with
-
-
:location
- overwrites the default redirect location used after a successful htmlpost
request. -
:action
- overwrites the default render action used after an unsuccessful htmlpost
request.
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