[ci skip]

Add descriptions about `ActiveRecord::Base#to_param` to

* `ActionDispatch::Routing::Base#match`
* Overriding Named Route Parameters (guide)

When passes `:param` to route definision, always `to_param` method of
related model is overridden to constructe an URL by passing these
model instance to named_helper.

1 files changed, 14 insertions, 0 deletions

diff --git a/guides/source/routing.md b/guides/source/routing.md
index 52f11f92bd..02763eabcd 100644
--- a/guides/source/routing.md
+++ b/guides/source/routing.md
@@ -1087,6 +1087,20 @@ edit_videos GET  /videos/:identifier/edit(.:format) videos#edit
 Video.find_by(identifier: params[:identifier])
 ```
 
+You can override `ActiveRecord::Base#to_param` of a related
+model to constructe an URL.
+
+```ruby
+class Video < ActiveRecord::Base
+  def to_param  # overridden
+    identifier
+  end
+end
+
+video = Video.find_by(identifier: "Roman-Holiday")
+edit_videos_path(video) # => "/videos/Roman-Holiday"
+```
+
 Inspecting and Testing Routes
 -----------------------------