Для статьи «Метапрограммирование в Ruby: разбор примера»

demo00.rb

# encoding: utf-8

require './prop00'

class Alpha
  property :alpha, :beta
  attr_accessor :gamma
end

a = Alpha.new

a.alpha = 1
a.beta = 2
a.gamma = 3

p [a.alpha, a.beta, a.gamma]
p a

demo01.rb

# encoding: utf-8

require './prop01'

class Alpha
  property :alpha, default: 100
  property :beta, default_proc: proc { |o| o.class.name }
  property :gamma, default_proc: :class
end

a = Alpha.new

p [a.alpha, a.beta, a.gamma]
p a

demo02.rb

# encoding: utf-8

require './prop02'

class Alpha
  property :alpha
  property :beta do |obj, prop, value|
    p [obj, prop, value]
  end
end

a = Alpha.new

a.alpha = 100
a.beta = 200

demo03.rb

# encoding: utf-8

require './prop03'

class Alpha

  property :alpha, filter: Integer
  property :beta, filter: proc { |x| Integer === x && x > 0 },
      on_invalid: StandardError

end

a = Alpha.new

a.alpha = 11
a.beta = 2

p a

a.alpha = "String"

p a

a.beta = -1

p a

prop00.rb

# encoding: utf-8

class Module

  private

  def prop name
    varnm = "@#{name}"
    getnm = name
    setnm = "#{name}="
    define_method getnm do
      instance_variable_get varnm
    end
    define_method setnm do |value|
      instance_variable_set varnm, value
    end
  end

  def property *names
    names.each do |nm|
      prop nm
    end
  end

end

prop01.rb

# encoding: utf-8

class Module

  private

  def prop name, default: nil, default_proc: nil
    varnm = "@#{name}"
    getnm = name
    setnm = "#{name}="
    define_method getnm do
      if ! instance_variable_defined?(varnm)
        if default_proc
          instance_variable_set varnm,
              default_proc.to_proc.call(self)
        else
          instance_variable_set varnm, default
        end
      end
      instance_variable_get varnm
    end
    define_method setnm do |value|
      instance_variable_set varnm, value
    end
  end

  def property *names, default: nil, default_proc: nil
    names.each do |nm|
      prop nm, default: default, default_proc: default_proc
    end
  end

end

prop02.rb

# encoding: utf-8

class Module

  private

  def prop name, default: nil, default_proc: nil, &block
    varnm = "@#{name}"
    getnm = name
    setnm = "#{name}="
    define_method getnm do
      if ! instance_variable_defined?(varnm)
        if default_proc
          instance_variable_set varnm,
              default_proc.to_proc.call(self)
        else
          instance_variable_set varnm, default
        end
      end
      instance_variable_get varnm
    end
    define_method setnm do |value|
      instance_variable_set varnm, value
      if block
        block.call self, name, value
      end
    end
  end

  def property *names, default: nil, default_proc: nil, &block
    names.each do |nm|
      prop nm, default: default, default_proc: default_proc, &block
    end
  end

end

prop03.rb

# encoding: utf-8

class Module

  private

  def prop name, default: nil, default_proc: nil, filter: nil, on_invalid: nil,
      &block
    varnm = "@#{name}"
    getnm = name
    setnm = "#{name}="
    if !(on_invalid == nil ||
      (Class === on_invalid && on_invalid <= Exception) || Proc === on_invalid)
      raise TypeError,
          "Invalid type of 'on_invalid' argument: #{on_invalid.class}", caller
    end
    define_method getnm do
      if ! instance_variable_defined?(varnm)
        if default_proc
          instance_variable_set varnm,
              default_proc.to_proc.call(self)
        else
          instance_variable_set varnm, default
        end
      end
      instance_variable_get varnm
    end
    define_method setnm do |value|
      if filter && !(filter === value)
        if Class === on_invalid && on_invalid <= Exception
          raise on_invalid,
              "Invalid property (#{name}) value: #{value.inspect}!", caller
        elsif Proc === on_invalid
          on_invalid.call self, name, value
        end
      else
        instance_variable_set varnm, value
        if block
          block.call self, name, value
        end
      end
    end
  end

  def property *names, default: nil, default_proc: nil, filter: nil,
      on_invalid: nil, &block
    names.each do |nm|
      prop nm, default: default, default_proc: default_proc, filter: filter,
          on_invalid: on_invalid, &block
    end
  end

end