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rails/polymorphic-path-helpers.md

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+# Polymorphic Path Helpers
+
+Underlying many of the path helpers that we use day to day when building out
+the views in our Rails apps are a set of methods in the
+[`ActionDispatch::Routing::PolymorphicRoutes`](http://api.rubyonrails.org/classes/ActionDispatch/Routing/PolymorphicRoutes.html)
+module.
+
+The `#polymorphic_path` method given an instance of a model will produce the
+relevant show path.
+
+```ruby
+> app.polymorphic_path(Article.first)
+  Article Load (0.5ms)  SELECT  "articles".* FROM "articles"  ORDER BY "articles"."id" ASC LIMIT 1
+=> "/articles/2"
+```
+
+Given just the model's constant, it will produce the index path.
+
+```ruby
+> app.polymorphic_path(Article)
+=> "/articles"
+```
+
+Additionally, there are variants with `edit_` and `new_` prefixed for
+generating the edit and new paths respectively.
+
+```ruby
+> app.edit_polymorphic_path(Article.first)
+  Article Load (0.6ms)  SELECT  "articles".* FROM "articles"  ORDER BY "articles"."id" ASC LIMIT 1
+=> "/articles/2/edit"
+> app.new_polymorphic_path(Article)
+=> "/articles/new"
+```