From: Raul Parolari <raulparolari@...>
Date: 2007-11-12T14:40:25+09:00
Subject: Re: Controlling attribute setting in a Struct


Uups, I treated the maximum as the "first invalid value"; correction:

class MyMaxBoundedStruct < Struct.new(:life, :strength, :charisma, 
:weapon)

  # class variable (depending on Spec, a Constant could be used)
  @@maximum = 1000

  arr = %w[life strength charisma weapon]

  arr.each do |m|
    define_method("#{m}=") do |val|
      if val <= @@maximum
        super(val)
      else
        raise ArgumentError, "#{m} set above maximum"
      end
    end
  end
end # class

rabbit = MyMaxBoundedStruct.new

rabbit.strength = 1000  # ok
rabbit.strength = 1001  # Argument: strength set above maximum
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