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vendor/rails/activesupport/lib/active_support/core_ext/module/attr_accessor_with_default.rb

 

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class Module

 

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  # Declare an attribute accessor with an initial default return value.

 

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  #

 

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  # To give attribute <tt>:age</tt> the initial value <tt>25</tt>:

 

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  #  

 

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  #   class Person

 

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  #     attr_accessor_with_default :age, 25

 

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  #   end

 

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  #

 

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  #   some_person.age

 

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  #   => 25

 

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  #   some_person.age = 26

 

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  #   some_person.age

 

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  #   => 26

 

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  #

 

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  # To give attribute <tt>:element_name</tt> a dynamic default value, evaluated

 

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  # in scope of self:

 

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  #

 

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  #   attr_accessor_with_default(:element_name) { name.underscore } 

 

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  #

 

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  def attr_accessor_with_default(sym, default = nil, &block)

 

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    raise 'Default value or block required' unless !default.nil? || block

 

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    define_method(sym, block_given? ? block : Proc.new { default })

 

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    module_eval(<<-EVAL, __FILE__, __LINE__)

 

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      def #{sym}=(value)                        # def age=(value)

 

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        class << self; attr_reader :#{sym} end  #   class << self; attr_reader :age end

 

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        @#{sym} = value                         #   @age = value

 

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      end                                       # end

 

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    EVAL

 

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  end

 

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end

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