在带有lambda的单个实例上重新定义单个ruby方法

问题描述：

在Ruby中，有没有一种方法可以使用proc重新定义类的特定实例的方法?例如:

In Ruby, is there a way to redefine a method of a particular instance of a class using a proc? For example:

class Foo
  def bar()
    return "hello"
  end
end

x = Foo.new
y = Foo.new

(类似):

y.method(:bar) = lambda { return "goodbye" }

x.bar
y.bar

制作:

hello
goodbye

谢谢.

答

def define_singleton_method_by_proc(obj, name, block)
  metaclass = class << obj; self; end
  metaclass.send(:define_method, name, block)
end
p = proc { "foobar!" }
define_singleton_method_by_proc(y, :bar, p)

或者，如果您想通过猴子修补对象来简化操作

or, if you want to monkey-patch Object to make it easy

class Object
  # note that this method is already defined in Ruby 1.9
  def define_singleton_method(name, callable = nil, &block)
    block ||= callable
    metaclass = class << self; self; end
    metaclass.send(:define_method, name, block)
  end
end

p = proc { "foobar!" }
y.define_singleton_method(:bar, p)
#or
y.define_singleton_method(:bar) do
   "foobar!"
end

或者，如果您想内联定义proc，则可能更易读

or, if you want to define your proc inline, this may be more readable

class << y
  define_method(:bar, proc { "foobar!" })
end

或

class << y
  define_method(:bar) { "foobar!" }
end

这是最易读的内容，但可能不符合您的需求

this is the most readable, but probably doesn't fit your needs

def y.bar
  "goodbye"
end

该问题与相关性很高

在带有lambda的单个实例上重新定义单个ruby方法

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