ruby - 在 Ruby 模块中继承常量

Question

在 Ruby 中，我正在尝试创建一个类，该类基于初始化期间给出的值，将从以下模块之一继承。我想创建一个基本模块，这两个模块都继承自该模块，其中包含使用继承它的模块中定义的常量的常用方法。示例:

module BaseMod
  def what_am_i
    puts OUTPUT
  end
end

module Tall
  OUTPUT = "I am tall"
  include BaseMod
end

module Short
  OUTPUT = "I am short"
  include BaseMod
end

class Person
  def initialize type
    if type =~ /short/i
      extend Short
    else
      extend Tall
    end
  end
end

p = Person.new "short"
p.what_am_i

我的问题是，当调用“p.what_am_i”时出现以下错误:

NameError: uninitialized constant BaseMod::OUTPUT
  const_missing at org/jruby/RubyModule.java:2642
      what_am_i at test_logic2.rb:3
         (root) at test_logic2.rb:28

我也想知道是否有更好的方法来做到这一点。

Answer 1

module BaseMod
  def what_am_i
    puts self.class::OUTPUT
  end
end

module Tall
  OUTPUT = "I am tall"
  include BaseMod
end

module Short
  OUTPUT = "I am short"
  include BaseMod
end

class Person
  def initialize(type)
    if type =~ /short/i
      self.class.send(:include, Short)
    else
      self.class.send(:include, Tall)
    end
  end
end

p = Person.new "short"
p.what_am_i

编辑:上面的代码实际上不起作用:

p = Person.new "short"
p.what_am_i
>> I am short
p = Person.new "tall"
p.what_am_i
>> I am tall
p = Person.new "short"
p.what_am_i
>> I am tall

这是另一种尝试:

module BaseMod
  def self.included(base)
    base.send(:define_method, :what_am_i) do
      puts base::OUTPUT
    end
  end
end

module Tall
  OUTPUT = "I am tall"
  include BaseMod
end

module Short
  OUTPUT = "I am short"
  include BaseMod
end

class Person
  def initialize type
    if type =~ /short/i
      extend Short
    else
      extend Tall
    end
  end
end

p = Person.new "short"
p.what_am_i
p = Person.new "tall"
p.what_am_i
p = Person.new "short"
p.what_am_i