Rails 3 - Restricting formats for action in resource routes

Question

I have a resource defined in my routes.

resources :categories

And I have the following in my Category controller:

  def show
    @category = Category.find(params[:id])

    respond_to do |format|
      format.json { render :json => @category }
      format.xml  { render :xml => @category }
    end
  end

The controller action works fine for json and xml. However I do NOT want the controller to respond to html format requests. How can I only allow json and xml? This should only happen in the show action.

What is the best way to achieve this? Also is there any good tips for DRYing up the respond_to block?

Thanks for your help.

Solution 1

I found that this seemed to work (thanks to @Pan for pointing me in the right direction):

resources :categories, :except => [:show]
resources :categories, :only => [:show], :defaults => { :format => 'json' }

The above seems to force the router into serving a format-less request, to the show action, as json by default.

Solution 2

You must wrap those routes in a scope if you want to restrict them to a specific format (e.g. html or json). Constraints unfortunately don't work as expected in this case.

This is an example of such a block...

scope :format => true, :constraints => { :format => 'json' } do
  get '/bar' => "bar#index_with_json"
end

More information can be found here: https://github.com/rails/rails/issues/5548

This answer is copied from my previous answer here..

Rails Routes - Limiting the available formats for a resource

Solution 3

You could do the following in your routes.rb file to make sure that only the show action is constrained to json or xml:

resources :categories, :except => [:show]
resources :categories, :only => [:show], :constraints => {:format => /(json|xml)/}

If this doesn't work you could try explicitly matching the action:

resources :categories, :except => [:show]
match 'categories/:id.:format' => 'categories#show', :constraints => {:format => /(json|xml)/}

Comments

[Mike]

Sorry, this didn't appear to work. Requesting an html page still responds.

[Pan Thomakos]

I added another more explicit alternative if the first option doesn't work for you.

[jwarzech]

This will still respond with the html template if the .html extension is added to the url.

[Kamil Jopek]

Thank you, this is very useful answer. Worked for me like a charm.

[koonse]

this will not limit requests to those formats, see my answer below for the correct implementation

[Pathogen]

The reason why the first part of this answer doesn't work, is that while it constrains the format it doesn't require that it be present. koonse's answer is better.

[Andrey Artemyev]

Only "constraints" or "defaults" doesn't work for me, this answer is right.