ri > ActionDispatch::Routing::PolymorphicRoutes

= ActionDispatch::Routing::PolymorphicRoutes

(from /home/chedong/.local/share/rdoc)
------------------------------------------------------------------------
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"
------------------------------------------------------------------------
= Instance methods:

  polymorphic_path
  polymorphic_url