Add docs with usage examples for ActiveModel::Model

Also add test to ensure basic model does not explode when
initialized with nil.

1 files changed, 19 insertions, 0 deletions

diff --git a/activemodel/README.rdoc b/activemodel/README.rdoc
index a7ba27ba73..9b121510a9 100644
--- a/activemodel/README.rdoc
+++ b/activemodel/README.rdoc
@@ -13,6 +13,25 @@ in code duplication and fragile applications that broke on upgrades. Active
 Model solves this by defining an explicit API. You can read more about the
 API in ActiveModel::Lint::Tests.
 
+Active Model provides a default module that implements the basic API required
+to integrate with Action Pack out of the box: +ActiveModel::Model+.
+
+    class Person
+      include ActiveModel::Model
+
+      attr_accessor :name, :age
+      validates_presence_of :name
+    end
+
+    person = Person.new(:name => 'bob', :age => '18')
+    person.name # => 'bob'
+    person.age # => 18
+    person.valid? # => false
+
+It includes model name instrospection, conversions, translations and
+validations, resulting in a class suitable to be used with ActionPack.
+See +ActiveModel::Model+ for more examples.
+
 Active Model also provides the following functionality to have ORM-like
 behavior out of the box: