Polymorphic URL helpers are methods for smart resolution to a named route call when given an Active Record model instance. They are to be used in combination with ActionController::Resources.

These methods are useful when you want to generate the correct URL or path to a RESTful resource without having to know the exact type of the record in question.

Nested resources and/or namespaces are also supported, as illustrated in the example:

polymorphic_url([:admin, @article, @comment])

results in:

admin_article_comment_url(@article, @comment)

Usage within the framework

Polymorphic URL helpers are used in a number of places throughout the Rails framework:

  • url_for, so you can use it with a record as the argument, e.g. url_for(@article);

  • ActionView::Helpers::FormHelper uses polymorphic_path, so you can write form_for(@article) without having to specify :url parameter for the form action;

  • redirect_to (which, in fact, uses url_for) so you can write redirect_to(post) in your controllers;

  • ActionView::Helpers::AtomFeedHelper, so you don't have to explicitly specify URLs for feed entries.

Prefixed polymorphic helpers

In addition to polymorphic_url and polymorphic_path methods, a number of prefixed helpers are available as a shorthand to action: "..." in options. Those are:

  • edit_polymorphic_url, edit_polymorphic_path

  • new_polymorphic_url, new_polymorphic_path

Example usage:

edit_polymorphic_path(@post)           # => "/posts/1/edit"
polymorphic_path(@post, format: :pdf)  # => "/posts/1.pdf"

Usage with mounted engines

If you are using a mounted engine and you need to use a polymorphic_url pointing at the engine's routes, pass in the engine's route proxy as the first argument to the method. For example:

polymorphic_url([blog, @post])  # calls blog.post_path(@post)
form_for([blog, @post])         # => "/blog/posts/1"

Methods

Instance Public methods

polymorphic_path(record_or_hash_or_array, options = {})

Returns the path component of a URL for the given record.

📝 Source code 
# File actionpack/lib/action_dispatch/routing/polymorphic_routes.rb, line 124
      def polymorphic_path(record_or_hash_or_array, options = {})
        if Hash === record_or_hash_or_array
          options = record_or_hash_or_array.merge(options)
          record  = options.delete :id
          return polymorphic_path record, options
        end

        if mapping = polymorphic_mapping(record_or_hash_or_array)
          return mapping.call(self, [record_or_hash_or_array, options], true)
        end

        opts   = options.dup
        action = opts.delete :action
        type   = :path

        HelperMethodBuilder.polymorphic_method self,
                                               record_or_hash_or_array,
                                               action,
                                               type,
                                               opts
      end
🔎 See on GitHub

polymorphic_url(record_or_hash_or_array, options = {})

Constructs a call to a named RESTful route for the given record and returns the resulting URL string. For example:

# calls post_url(post)
polymorphic_url(post) # => "http://example.com/posts/1"
polymorphic_url([blog, post]) # => "http://example.com/blogs/1/posts/1"
polymorphic_url([:admin, blog, post]) # => "http://example.com/admin/blogs/1/posts/1"
polymorphic_url([user, :blog, post]) # => "http://example.com/users/1/blog/posts/1"
polymorphic_url(Comment) # => "http://example.com/comments"

Options

  • :action - Specifies the action prefix for the named route: :new or :edit. Default is no prefix.

  • :routing_type - Allowed values are :path or :url. Default is :url.

Also includes all the options from url_for. These include such things as :anchor or :trailing_slash. Example usage is given below:

polymorphic_url([blog, post], anchor: 'my_anchor')
  # => "http://example.com/blogs/1/posts/1#my_anchor"
polymorphic_url([blog, post], anchor: 'my_anchor', script_name: "/my_app")
  # => "http://example.com/my_app/blogs/1/posts/1#my_anchor"

For all of these options, see the documentation for url_for.

Functionality

# an Article record
polymorphic_url(record)  # same as article_url(record)

# a Comment record
polymorphic_url(record)  # same as comment_url(record)

# it recognizes new records and maps to the collection
record = Comment.new
polymorphic_url(record)  # same as comments_url()

# the class of a record will also map to the collection
polymorphic_url(Comment) # same as comments_url()
📝 Source code 
# File actionpack/lib/action_dispatch/routing/polymorphic_routes.rb, line 101
      def polymorphic_url(record_or_hash_or_array, options = {})
        if Hash === record_or_hash_or_array
          options = record_or_hash_or_array.merge(options)
          record  = options.delete :id
          return polymorphic_url record, options
        end

        if mapping = polymorphic_mapping(record_or_hash_or_array)
          return mapping.call(self, [record_or_hash_or_array, options], false)
        end

        opts   = options.dup
        action = opts.delete :action
        type   = opts.delete(:routing_type) || :url

        HelperMethodBuilder.polymorphic_method self,
                                               record_or_hash_or_array,
                                               action,
                                               type,
                                               opts
      end
🔎 See on GitHub