Question

Reading this: http://guides.rubyonrails.org/routing.html#adding-more-restful-actions

What does it mean to add a ‘member route’?

or do add a route to the collection?

What is a member and a collection when talking about routes?

Answer 1

They’re both ways to add additional actions to a resource-based route in Rails.

• A member route requires an ID, because it acts on a member.
• A collection route doesn’t require an ID because it acts on a collection of objects.

I like to think of them in terms of RESTful URLs. Consider the basics for a resource/model Foo

GET    /foo            # FooController#index
GET    /foo/:id        # FooController#show
GET    /foo/new        # FooController#new
POST   /foo            # FooController#create
GET    /foo/:id/edit   # FooController#edit
PUT    /foo/:id        # FooController#update
DELETE /foo/:id        # FooController#destroy

Notice how:

• Some routes have :id placeholders for Foo.id, and so refer to a specific Foo
• Some routes have no :id, and thus refer to all Foos (and/or no specific foo, as in #new and #create)
• Some routes (index/create, show/update/destroy) have the same URL, and use HTTP methods to differentiate between them
• Some routes (edit/show) are basically the same (method & URL prefix) except for a different suffix (including “no suffix”) at the end.

Member routes and collection routes let you add additional routes/actions using the same techniques as I listed above.

A member route adds a custom action to a specific instance using the URL suffix and HTTP method you provide. So, if you had a member route declaration of :member => { :bar => :get }. you’d get an additional route of:

GET    /foo/:id/bar # FooController#bar

Note how it overloads GET /foo/:id in the same way that `edit’ does. This is how you’d implement a “delete” action that provides a UI for the “destroy” action.

Similarly, a collection route adds an overload to the collection and/or a non-specific instance (it’s up to you to decide exactly what it implies). So, if you declared :collection => { :baz => :get }, you’d get an additional route:

GET    /foo/baz        # FooController#baz

…in very much the same way as new.

You can also customize the HTTP method.

For example, I just recently had a project where I needed a “reply” action on a Comment. It’s basically the same idea as Comment#create (which uses POST), except that it’s in reference to a specific parent Comment. So, I created a member route: :member => { :reply => :post }. This gave me:

POST   /comment/:id/reply   # CommentController#reply

This keeps the routes restful while still expanding upon the basic 7 actions.