method

attr_accessor_with_default

v3.0.9 - Show latest stable - Class: Module

attr_accessor_with_default(sym, default = nil, &block)

public

Declare an attribute accessor with an initial default return value.

To give attribute :age the initial value 25:

class Person
  attr_accessor_with_default :age, 25
end

some_person.age
=> 25
some_person.age = 26
some_person.age
=> 26

To give attribute :element_name a dynamic default value, evaluated in scope of self:

attr_accessor_with_default(:element_name) { name.underscore }

# File activesupport/lib/active_support/core_ext/module/attr_accessor_with_default.rb, line 21
  def attr_accessor_with_default(sym, default = nil, &block)
    raise 'Default value or block required' unless !default.nil? || block
    define_method(sym, block_given? ? block : Proc.new { default })
    module_eval(      def #{sym}=(value)                        # def age=(value)        class << self; attr_reader :#{sym} end  #   class << self; attr_reader :age end        @#{sym} = value                         #   @age = value      end                                       # end, __FILE__, __LINE__ + 1)
  end

1Note

Some unexpected behaviour

stevo · Sep 13, 20111 thank

When using Array as default value, it behaves more like cattr_accessor...

class A

attr_accessor_with_default :b, [] end

x = A.new
x.b << 1

#puts x.b.inspect => [1]

y = A.new
y.b << 2

#puts y.b.inspect => [1, 2]

attr_accessor_with_default

1Note

Some unexpected behaviour

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