Closes #4

README.textile

@@ -351,6 +351,32 @@ for the current user.
 
 NOTE: The logic for deciding which comments a user should see still belongs in the model layer. In general, you should encapsulate concerns that require making direct Active Record queries in scopes or public methods on your models.
 
+h4. Modifying Associations
+
+You can also rename associations if required. Say for example you have an association that
+makes sense to be named one thing in your code, but another when data is serialized.
+You can use the <code>:as</code> option to specify a different name for an association. 
+Here is an exmaple:
+
+<pre lang="ruby">
+class UserSerializer < ActiveModel::Serializer
+  has_many :followed_posts, :as => :posts
+  has_one :owne_account, :as => :account
+end
+</pre>
+
+Using the <code>:as</code> without a <code>:serializer</code> option will use implicit detection
+to determine a serializer. In this example, you'd have to define two classes: <code>PostSerializer</code>
+and <code>AccountSerializer</code>. You can also add the <code>:serializer</code> option
+to set it explicitly:
+
+<pre lang="ruby">
+class UserSerializer < ActiveModel::Serializer
+  has_many :followed_posts, :as => :posts, :serializer => CustomPostSerializer
+  has_one :owne_account, :as => :account, :serializer => PrivateAccountSerializer
+end
+</pre>
+
 h3. Customizing Associations
 
 Not all front-ends expect embedded documents in the same form. In these cases, you can override the
@@ -431,6 +457,7 @@ The +association_ids+ helper will use the overridden version of the association,
 this case, +association_ids+ will only include the ids of the comments provided by the
 +comments+ method.
 
+
 h3. Special Association Serializers
 
 So far, associations defined in serializers use either the +as_json+ method on the model

lib/active_model/serializer.rb

@@ -68,6 +68,10 @@ module ActiveModel
         def serializer
           options[:serializer]
         end
+
+        def key
+          options[:as] || name
+        end
       end
 
       class HasMany < Config #:nodoc:
@@ -122,7 +126,14 @@ module ActiveModel
             class_eval "def #{attr}() object.#{attr} end", __FILE__, __LINE__
           end
 
-          options[:serializer] ||= const_get("#{attr.to_s.camelize}Serializer")
+          # if :as is specified without :serializer, then use conventions
+          # to determine the serializer
+          if options[:as] && !options[:serializer]
+            options[:serializer] = const_get("#{options[:as].to_s.camelize.singularize}Serializer")
+          else
+            options[:serializer] ||= const_get("#{attr.to_s.camelize}Serializer")
+          end
+
           klass.new(attr, options)
         end
       end
@@ -212,7 +223,7 @@ module ActiveModel
 
       _associations.each do |association|
         associated_object = send(association.name)
-        hash[association.name] = association.serialize(associated_object, scope)
+        hash[association.key] = association.serialize(associated_object, scope)
       end
 
       hash
@@ -225,7 +236,7 @@ module ActiveModel
 
       _associations.each do |association|
         associated_object = send(association.name)
-        hash[association.name] = association.serialize_ids(associated_object, scope)
+        hash[association.key] = association.serialize_ids(associated_object, scope)
       end
 
       hash
@@ -250,4 +261,4 @@ class Array
   def active_model_serializer
     ActiveModel::ArraySerializer
   end
-end
+end

test/serializer_test.rb

@@ -34,6 +34,11 @@ class SerializerTest < ActiveModel::TestCase
   end
 
   class Post < Model
+    def initialize(attributes)
+      super(attributes)
+      self.comments ||= []
+    end
+
     attr_accessor :comments
     def active_model_serializer; PostSerializer; end
   end
@@ -429,4 +434,78 @@ class SerializerTest < ActiveModel::TestCase
       { :comment => { :title => "Comment1" } }
     ], serializer.as_json)
   end
-end
+
+  class CustomBlog < Blog
+    attr_accessor :public_posts, :public_user
+  end
+
+  class CustomBlogSerializer < ActiveModel::Serializer
+    has_many :public_posts, :as => :posts, :serializer => PostSerializer
+    has_one :public_user, :as => :user, :serializer => UserSerializer
+  end
+
+  def test_associations_with_as
+    posts = [
+      Post.new(:title => 'First Post', :body => 'text'), 
+      Post.new(:title => 'Second Post', :body => 'text')
+    ]
+    user = User.new
+
+    custom_blog = CustomBlog.new
+    custom_blog.public_posts = posts
+    custom_blog.public_user = user
+
+    serializer = CustomBlogSerializer.new(custom_blog, :scope => true)
+
+    assert_equal({
+      :custom_blog => {
+        :posts => [
+          {:title => 'First Post', :body => 'text', :comments => []},
+          {:title => 'Second Post', :body => 'text', :comments => []}
+        ],
+        :user => {
+          :first_name => "Jose", 
+          :last_name => "Valim", :ok => true, 
+          :scope => true
+        }
+      }
+    }, serializer.as_json)
+  end
+
+  def test_implicity_detection_for_association_serializers 
+    implicit_serializer = Class.new(ActiveModel::Serializer) do
+      root :custom_blog
+      const_set(:UserSerializer, UserSerializer)
+      const_set(:PostSerializer, PostSerializer)
+
+      has_many :public_posts, :as => :posts
+      has_one :public_user, :as => :user
+    end
+
+    posts = [
+      Post.new(:title => 'First Post', :body => 'text', :comments => []), 
+      Post.new(:title => 'Second Post', :body => 'text', :comments => [])
+    ]
+    user = User.new
+
+    custom_blog = CustomBlog.new
+    custom_blog.public_posts = posts
+    custom_blog.public_user = user
+
+    serializer = implicit_serializer.new(custom_blog, :scope => true)
+
+    assert_equal({
+      :custom_blog => {
+        :posts => [
+          {:title => 'First Post', :body => 'text', :comments => []},
+          {:title => 'Second Post', :body => 'text', :comments => []}
+        ],
+        :user => {
+          :first_name => "Jose", 
+          :last_name => "Valim", :ok => true, 
+          :scope => true
+        }
+      }
+    }, serializer.as_json)
+  end
+end