# module ActionDispatch::Routing::PolymorphicRoutes

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 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"

## Using with mounted engines¶ ↑

If you use mounted engine, there is a possibility that you will need to use #polymorphic_url pointing at engine’s routes. To do that, just pass proxy used to reach engine’s routes as a first argument:

For example:

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

### Public Instance Methods

polymorphic_path(record_or_hash_or_array, options = {}) click to toggle source

Returns the path component of a URL for the given record. It uses `polymorphic_url` with `:routing_type => :path`.

    # File lib/action_dispatch/routing/polymorphic_routes.rb, line 134
    def polymorphic_path(record_or_hash_or_array, options = {})
      polymorphic_url(record_or_hash_or_array, options.merge(:routing_type => :path))
    end

polymorphic_url(record_or_hash_or_array, options = {}) click to toggle source

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`.

#### Examples¶ ↑

    # 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()

    # File lib/action_dispatch/routing/polymorphic_routes.rb, line 90
    def polymorphic_url(record_or_hash_or_array, options = {})
      if record_or_hash_or_array.kind_of?(Array)
        record_or_hash_or_array = record_or_hash_or_array.compact
        if record_or_hash_or_array.first.is_a?(ActionDispatch::Routing::RoutesProxy)
          proxy = record_or_hash_or_array.shift
        end
        record_or_hash_or_array = record_or_hash_or_array[0] if record_or_hash_or_array.size == 1
      end

      record = extract_record(record_or_hash_or_array)
      record = convert_to_model(record)

      args = Array === record_or_hash_or_array ?
        record_or_hash_or_array.dup :
        [ record_or_hash_or_array ]

      inflection = if options[:action] && options[:action].to_s == "new"
        args.pop
        :singular
      elsif (record.respond_to?(:persisted?) && !record.persisted?)
        args.pop
        :plural
      elsif record.is_a?(Class)
        args.pop
        :plural
      else
        :singular
      end

      args.delete_if {|arg| arg.is_a?(Symbol) || arg.is_a?(String)}
      named_route = build_named_route_call(record_or_hash_or_array, inflection, options)

      url_options = options.except(:action, :routing_type)
      unless url_options.empty?
        args.last.kind_of?(Hash) ? args.last.merge!(url_options) : args << url_options
      end

      args.collect! { |a| convert_to_model(a) }

      (proxy || self).send(named_route, *args)
    end