在
Ruby中,我正在尝试创建一个类,它基于初始化期间给出的值将继承以下模块之一.我想创建一个基本模块,这些模块继承自包含常用方法的基本模块,这些方法使用继承它的模块中定义的常量.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,我收到以下错误:
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这件事.
解决方法
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