Define a predicate method for boolean attributes

activemodel/CHANGELOG.md

@@ -1,3 +1,23 @@
+*   Boolean attributes defined with the `ActiveModel::Attributes` API will now
+    have their respective predicate method defined automatically.
+
+    For example:
+
+    ```ruby
+    class Person
+      include ActiveModel::Attributes
+
+      attribute :loves_rails, :boolean
+    end
+
+    person = Person.new
+    person.love_rails?  # => false
+    person.love_rails = true
+    person.love_rails?  # => true
+    ```
+
+    *Connor McQuillan*
+
 *   Custom attribute types that inherit from Active Model built-in types and do
     not override the `serialize` method will now benefit from an optimization
     when serializing attribute values for the database.

activemodel/lib/active_model/attribute_registration.rb

@@ -16,6 +16,7 @@ def attribute(name, type = nil, default: (no_default = true), **options)
         pending.type = type if type
         pending.default = default unless no_default
 
+        define_predicate_method(name) if type.is_a?(ActiveModel::Type::Boolean)
         reset_default_attributes
       end
 
@@ -72,6 +73,10 @@ def resolve_attribute_name(name)
         def resolve_type_name(name, **options)
           Type.lookup(name, **options)
         end
+
+        def define_predicate_method(name)
+          define_method("#{name}?") { public_send(name) == true }
+        end
     end
   end
 end

activemodel/test/cases/attributes_test.rb

@@ -115,6 +115,20 @@ def attribute=(_, _)
       end
     end
 
+    test "boolean attributes define predicate methods" do
+      model = ModelForAttributesTest.new(boolean_field: "1")
+
+      assert_equal true, model.boolean_field?
+
+      model.boolean_field = "false"
+
+      assert_equal false, model.boolean_field?
+
+      model.boolean_field = nil
+
+      assert_equal false, model.boolean_field?
+    end
+
     test "children inherit attributes" do
       data = ChildModelForAttributesTest.new(integer_field: "4.4")