Implement mattr_acessor :default option

activesupport/CHANGELOG.md

@@ -1,3 +1,12 @@
+*   Add default option to module and class attribute accessors.
+
+       mattr_accessor :settings, default: {}
+
+    Works for `mattr_reader`, `mattr_writer`, `cattr_accessor`, `cattr_reader`,
+    and `cattr_writer` as well.
+
+    *Genadi Samokovarov*
+
 *   Add `Date#prev_occurring` and `Date#next_occurring` to return specified next/previous occurring day of week.
 
     *Shota Iguchi*

activesupport/lib/active_support/core_ext/module/attribute_accessors.rb

@@ -38,13 +38,10 @@ class Module
   #
   #   Person.new.hair_colors # => NoMethodError
   #
-  #
-  # Also, you can pass a block to set up the attribute with a default value.
+  # You can set a default value for the attribute.
   #
   #   module HairColors
-  #     mattr_reader :hair_colors do
-  #       [:brown, :black, :blonde, :red]
-  #     end
+  #     mattr_reader :hair_colors, default: [:brown, :black, :blonde, :red]
   #   end
   #
   #   class Person
@@ -52,8 +49,7 @@ class Module
   #   end
   #
   #   Person.new.hair_colors # => [:brown, :black, :blonde, :red]
-  def mattr_reader(*syms)
-    options = syms.extract_options!
+  def mattr_reader(*syms, instance_reader: true, instance_accessor: true, default: nil)
     syms.each do |sym|
       raise NameError.new("invalid attribute name: #{sym}") unless /\A[_A-Za-z]\w*\z/.match?(sym)
       class_eval(<<-EOS, __FILE__, __LINE__ + 1)
@@ -64,14 +60,16 @@ class Module
         end
       EOS
 
-      unless options[:instance_reader] == false || options[:instance_accessor] == false
+      if instance_reader && instance_accessor
         class_eval(<<-EOS, __FILE__, __LINE__ + 1)
           def #{sym}
             @@#{sym}
           end
         EOS
       end
-      class_variable_set("@@#{sym}", yield) if block_given?
+
+      sym_default_value = (block_given? && default.nil?) ? yield : default
+      class_variable_set("@@#{sym}", sym_default_value) unless sym_default_value.nil?
     end
   end
   alias :cattr_reader :mattr_reader
@@ -107,12 +105,10 @@ class Module
   #
   #   Person.new.hair_colors = [:blonde, :red] # => NoMethodError
   #
-  # Also, you can pass a block to set up the attribute with a default value.
+  # You can set a default value for the attribute.
   #
   #   module HairColors
-  #     mattr_writer :hair_colors do
-  #       [:brown, :black, :blonde, :red]
-  #     end
+  #     mattr_writer :hair_colors, default: [:brown, :black, :blonde, :red]
   #   end
   #
   #   class Person
@@ -120,8 +116,7 @@ class Module
   #   end
   #
   #   Person.class_variable_get("@@hair_colors") # => [:brown, :black, :blonde, :red]
-  def mattr_writer(*syms)
-    options = syms.extract_options!
+  def mattr_writer(*syms, instance_writer: true, instance_accessor: true, default: nil)
     syms.each do |sym|
       raise NameError.new("invalid attribute name: #{sym}") unless /\A[_A-Za-z]\w*\z/.match?(sym)
       class_eval(<<-EOS, __FILE__, __LINE__ + 1)
@@ -132,14 +127,16 @@ class Module
         end
       EOS
 
-      unless options[:instance_writer] == false || options[:instance_accessor] == false
+      if instance_writer && instance_accessor
         class_eval(<<-EOS, __FILE__, __LINE__ + 1)
           def #{sym}=(obj)
             @@#{sym} = obj
           end
         EOS
       end
-      send("#{sym}=", yield) if block_given?
+
+      sym_default_value = (block_given? && default.nil?) ? yield : default
+      send("#{sym}=", sym_default_value) unless sym_default_value.nil?
     end
   end
   alias :cattr_writer :mattr_writer
@@ -197,12 +194,10 @@ class Module
   #   Person.new.hair_colors = [:brown]  # => NoMethodError
   #   Person.new.hair_colors             # => NoMethodError
   #
-  # Also you can pass a block to set up the attribute with a default value.
+  # You can set a default value for the attribute.
   #
   #   module HairColors
-  #     mattr_accessor :hair_colors do
-  #       [:brown, :black, :blonde, :red]
-  #     end
+  #     mattr_accessor :hair_colors, default: [:brown, :black, :blonde, :red]
   #   end
   #
   #   class Person
@@ -210,9 +205,9 @@ class Module
   #   end
   #
   #   Person.class_variable_get("@@hair_colors") # => [:brown, :black, :blonde, :red]
-  def mattr_accessor(*syms, &blk)
-    mattr_reader(*syms, &blk)
-    mattr_writer(*syms)
+  def mattr_accessor(*syms, instance_reader: true, instance_writer: true, instance_accessor: true, default: nil, &blk)
+    mattr_reader(*syms, instance_reader: instance_reader, instance_accessor: instance_accessor, default: default, &blk)
+    mattr_writer(*syms, instance_writer: instance_writer, instance_accessor: instance_accessor, default: default)
   end
   alias :cattr_accessor :mattr_accessor
 end

activesupport/test/core_ext/module/attribute_accessor_test.rb

@@ -12,7 +12,14 @@ class ModuleAttributeAccessorTest < ActiveSupport::TestCase
       cattr_accessor(:defa) { "default_accessor_value" }
       cattr_reader(:defr) { "default_reader_value" }
       cattr_writer(:defw) { "default_writer_value" }
+      cattr_accessor(:deff) { false }
       cattr_accessor(:quux) { :quux }
+
+      cattr_accessor :def_accessor, default: "default_accessor_value"
+      cattr_reader :def_reader, default: "default_reader_value"
+      cattr_writer :def_writer, default: "default_writer_value"
+      cattr_accessor :def_false, default: false
+      cattr_accessor(:def_priority, default: false) { :no_priority }
     end
     @class = Class.new
     @class.instance_eval { include m }
@@ -24,6 +31,21 @@ class ModuleAttributeAccessorTest < ActiveSupport::TestCase
     assert_nil @object.foo
   end
 
+  def test_mattr_default_keyword_arguments
+    assert_equal "default_accessor_value", @module.def_accessor
+    assert_equal "default_reader_value", @module.def_reader
+    assert_equal "default_writer_value", @module.class_variable_get(:@@def_writer)
+  end
+
+  def test_mattr_can_default_to_false
+    assert_equal false, @module.def_false
+    assert_equal false, @module.deff
+  end
+
+  def test_mattr_default_priority
+    assert_equal false, @module.def_priority
+  end
+
   def test_should_set_mattr_value
     @module.foo = :test
     assert_equal :test, @object.foo
@@ -91,9 +113,23 @@ class ModuleAttributeAccessorTest < ActiveSupport::TestCase
     assert_equal "default_writer_value", @module.class_variable_get("@@defw")
   end
 
-  def test_should_not_invoke_default_value_block_multiple_times
+  def test_method_invocation_should_not_invoke_the_default_block
     count = 0
+
     @module.cattr_accessor(:defcount) { count += 1 }
+
     assert_equal 1, count
+    assert_no_difference "count" do
+      @module.defcount
+    end
+  end
+
+  def test_declaring_multiple_attributes_at_once_invokes_the_block_multiple_times
+    count = 0
+
+    @module.cattr_accessor(:defn1, :defn2) { count += 1 }
+
+    assert_equal 1, @module.defn1
+    assert_equal 2, @module.defn2
   end
 end