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 writeform_for(@article)
without having to specify:url
parameter 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:
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"
Returns the path component of a URL for the given record. It uses
polymorphic_url
with routing_type: :path
.
# File actionpack/lib/action_dispatch/routing/polymorphic_routes.rb, line 123 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 opts = options.dup action = opts.delete :action type = :path HelperMethodBuilder.polymorphic_method self, record_or_hash_or_array, action, type, opts end
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()
# File actionpack/lib/action_dispatch/routing/polymorphic_routes.rb, line 103 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 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