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Add Module#attr_accessor_with_default to initialize value of attribut…

…e before setting it. Closes #6538. [Stuart Halloway, Marcel Molina Jr.]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@5539 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
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1 parent 0100a79 commit 309a6bd550281b60f25be28ea76a5cce5f9b377b Marcel Molina committed Nov 16, 2006
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2 activesupport/CHANGELOG
@@ -1,5 +1,7 @@
*SVN*
+* Add Module#attr_accessor_with_default to initialize value of attribute before setting it. Closes #6538. [Stuart Halloway, Marcel Molina Jr.]
+
* Hash#to_xml handles keys with the same name as Kernel methods. #6613 [Catfish]
* Added Time#end_of_day to get 23:59:59 of that day [DHH]
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1 activesupport/lib/active_support/core_ext/module.rb
@@ -1,6 +1,7 @@
require File.dirname(__FILE__) + '/module/inclusion'
require File.dirname(__FILE__) + '/module/attribute_accessors'
require File.dirname(__FILE__) + '/module/attr_internal'
+require File.dirname(__FILE__) + '/module/attr_accessor_with_default'
require File.dirname(__FILE__) + '/module/delegation'
require File.dirname(__FILE__) + '/module/introspection'
require File.dirname(__FILE__) + '/module/loading'
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31 activesupport/lib/active_support/core_ext/module/attr_accessor_with_default.rb
@@ -0,0 +1,31 @@
+class Module
+ # Declare an attribute accessor with an initial default return value.
+ #
+ # To give attribute <tt>:age</tt> the initial value <tt>25</tt>:
+ #
+ # class Person
+ # attr_accessor_with_default :age, 25
+ # end
+ #
+ # some_person.age
+ # => 25
+ # some_person.age = 26
+ # some_person.age
+ # => 26
+ #
+ # To give attribute <tt>:element_name</tt> a dynamic default value, evaluated
+ # in scope of self:
+ #
+ # attr_accessor_with_default(:element_name) { name.underscore }
+ #
+ def attr_accessor_with_default(sym, default = nil, &block)
+ raise 'Default value or block required' unless default || block
+ define_method(sym, block_given? ? block : Proc.new { default })
+ module_eval(<<-EVAL, __FILE__, __LINE__)
+ def #{sym}=(value)
+ class << self; attr_reader :#{sym} end
+ @#{sym} = value
+ end
+ EVAL
+ end
+end
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30 activesupport/test/core_ext/module/attr_accessor_with_default.rb
@@ -0,0 +1,30 @@
+require File.dirname(__FILE__) + '/../../abstract_unit'
+
+class AttrWithDefaultTest < Test::Unit::TestCase
+ def setup
+ @target = Class.new do
+ def helper
+ 'helper'
+ end
+ end
+ @instance = @target.new
+ end
+
+ def test_default_arg
+ @target.attr_accessor_with_default :foo, :bar
+ assert_equal(:bar, @instance.foo)
+ @instance.foo = nil
+ assert_nil(@instance.foo)
+ end
+
+ def test_default_proc
+ @target.attr_accessor_with_default(:foo) {helper.upcase}
+ assert_equal('HELPER', @instance.foo)
+ @instance.foo = nil
+ assert_nil(@instance.foo)
+ end
+
+ def test_invalid_args
+ assert_raise(RuntimeError) {@target.attr_accessor_with_default :foo}
+ end
+end

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