Adds documentation for overriding default serializer based on conditions (#1730)

suggested changes

update changelog

Author: cgmckeever

CHANGELOG.md

@@ -22,6 +22,7 @@ Fixes:
 
 Misc:
 - [#1673](https://github.com/rails-api/active_model_serializers/pull/1673) Adds "How to" guide on using AMS with POROs (@DrSayre)
+- [#1730](https://github.com/rails-api/active_model_serializers/pull/1730) Adds documentation for overriding default serializer based on conditions (@groyoh/@cgmckeever)
 
 ### [v0.10.0.rc5 (2016-04-04)](https://github.com/rails-api/active_model_serializers/compare/v0.10.0.rc4...v0.10.0.rc5)
 

docs/general/serializers.md

@@ -370,3 +370,19 @@ class PostSerializer < ActiveModel::Serializer
   end
 end
 ```
+
+## Overriding association serializer lookup
+
+If you want to define a specific serializer lookup for your associations, you can override
+the `ActiveModel::Serializer.serializer_for` method to return a serializer class based on defined conditions.
+
+```ruby
+class MySerializer < ActiveModel::Serializer
+  def self.serializer_for(model, options)
+    return SparseAdminSerializer if model.class == 'Admin'
+    super
+  end
+
+  # the rest of the serializer
+end
+```