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:
1 | polymorphic_url([:admin, @article, @comment]) |
results in:
1 | 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 writeform_for(@article)without having to specify:urlparameter for the form action; -
redirect_to(which, in fact, usesurl_for) so you can writeredirect_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:
1 2 | 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:
1 2 | polymorphic_url([blog, @post]) # calls blog.post_path(@post)form_for([blog, @post]) # => "/blog/posts/1" |