让ruby对象响应任意消息？

发布时间：2020-12-17 01:44:51 所属栏目：百科来源：网络整理

导读：在 ruby中是否有等效的 python __getattr__(至少可以找到方法)？ class X(object): def __getattr__(self,name): return lambda x: print("Calling " + name + ": " + x)x = X()x.some_method("some args") 所以它可能是这样的： class X # .. ??? .. def de

在 ruby中是否有等效的 python __getattr__(至少可以找到方法)？

class X(object):
    def __getattr__(self,name):
        return lambda x: print("Calling " + name + ": " + x)

x = X()
x.some_method("some args")

所以它可能是这样的：

class X
    # .. ??? ..
    def default_action(method_name,x)
        puts "Calling {method_name}: {x}"
    end
end

x = X.new()
x.some_method("some args")

解决方法

是.如果对象没有响应消息,Ruby将发送带有消息选择器的method_missing消息和接收者的参数：

class X
  def method_missing(selector,*args,&blk)
    puts "The message was #{selector.inspect}."
    puts "The arguments were #{args.map(&:inspect).join(',')}."
    puts "And there was #{blk ? 'a' : 'no'} block."
    super
  end
end

x = X.new
x.some_method('some args',:some_other_args,42)
# The message was :some_method.
# The arguments were "some args",42.
# And there was no block.
# NoMethodError: undefined method `some_method'

x.some_other_method do end
# The message was :some_other_method.
# The arguments were .
# And there was a block.
# NoMethodError: undefined method `some_other_method'

请注意,如果定义method_missing,还应该定义respond_to_missing？因此.否则你会得到这样的奇怪行为：

x.respond_to?(:foo) # => false
x.foo               # Works. Huh?

在这种特殊情况下,我们处理所有消息,因此我们可以简单地定义如下：

class X; def respond_to_missing?(*) true end end

x.respond_to?(:foo) # => true

（编辑：李大同）

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