我试图定义一个带有方法的类,以及一个缺少这些方法的类,然后允许后一个类的对象从前一个类的实例“学习”这些方法。
这是我的尝试 (Ruby 1.9.2) - 当我尝试更改 lambda 绑定(bind)中“self”的值时,它中断了(在注释为“BREAKS!”的行处)。
如果您能想出如何解决这个问题 - 我很想知道。
class Skill
attr_accessor :name
attr_accessor :technique
def initialize(name, &technique_proc)
@name = name
@technique = lambda(&proc)
end
end
class Person
attr_accessor :name
def initialize(name)
@name = name
end
def method_missing(m, *args)
"#{@name} the #{self.class}: I don't know how to #{m}"
end
def learn_skill(skill)
puts "#{@name} the #{self.class} is learning skill: #{skill.name}"
actual_self = self
eval "self = #{actual_self}", skill.technique.binding ####### BREAKS!
define_singleton_method skill.name.to_sym, skill.technique
end
def teach_skill(skill_name)
skill = nil
if self.respond_to?(skill_name)
puts "#{@name} the #{self.class} is teaching skill: #{skill_name}"
skill_method = self.method(skill_name.to_sym)
skill_proc = skill_method.to_proc
skill_lambda = lambda(&skill_proc)
skill = Skill.new(skill_name, &skill_lambda)
end
skill
end
end
class Teacher < Person
def speak(sentence)
"#{@name} the #{self.class} is now saying \"#{sentence}\"!"
end
def jump(number_of_feet)
"#{name} the #{self.class} is now jumping #{number_of_feet} high!"
end
end
miss_mollyflop = Teacher.new("Miss Mollyflop")
little_billey = Person.new("Little Billy")
puts miss_mollyflop.speak("Good morning, children!")
puts little_billey.speak("Good morning, Miss Mollyflop!")
speak_skill = miss_mollyflop.teach_skill("speak")
little_billey.learn_skill(speak_skill)
puts little_billey.speak("Good morning, Miss Mollyflop!")
这个的输出是:
Miss Mollyflop the Teacher is now saying "Good morning, children!"!
Little Billy the Person: I don't know how to speak
Miss Mollyflop the Teacher is teaching skill: speak
Little Billy the Person is learning skill: speak
test.rb:27:in `eval': (eval):1: Can't change the value of self (SyntaxError)
self = #<Person:0x1482270>
^
(eval):1: syntax error, unexpected $end
self = #<Person:0x1482270>
^
from test.rb:27:in `learn_skill'
from test.rb:64:in `<main>'
最佳答案
如果您想将方法从一个类复制到另一个类,这是可能的,但是如果该方法修改状态,它将修改原始对象的状态,而不是该方法随后绑定(bind)到的对象的状态(这是因为该方法不是'不是真的复制而是将方法的 Proc 包装器作为方法绑定(bind)到新对象):
a = Object.new
def a.hello
puts "hello world from a"
end
b = Object.new
b.define_singleton_method(:hello, &a.method(:hello))
b.hello #=> "hello world from a"
关于ruby - 我们如何在不同的 Ruby 类之间复制单例方法?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/4390329/