gistfile1

#!/usr/bin/env ruby

module ValidatedAccessor

  # Usage:
  #
  # class Foo
  #   include ValidatedAccessor
  #   attr_validated_accessor(:bar, :baz) { |x| x.between? 1, 10 }
  # end
  #
  # f = Foo.new
  # f.bar = 5
  # f.bar = 12  <--  Exception!

  def attr_validated_accessor(*syms, &block)

    raise 'Validation criteria in block required' unless block

    syms.each do |sym|

      module_eval do

        # Give us a standard reader.

        attr_reader sym

        # Define a writer that's special.

        define_method("#{sym}=") do |value|

          raise ArgumentError if !block.call(value)
          instance_variable_set "@#{sym}", value

        end
      end
    end

    # Return nil from the attr_validated_accessor call.

    nil

  end
end

# Test it out!

class Foo
  include ValidatedAccessor
  attr_validated_accessor(:bar, :baz) { |x| x.between? 1, 10 }
end

f = Foo.new

f.bar = 1
f.baz = 2
puts f.bar
puts f.baz

begin
  f.bar = 11
rescue ArgumentError
  puts 'Got an argument error'
end

begin
  f.baz = -1
rescue ArgumentError
  puts 'Got another argument error'
end