Question

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")

Answer 1

是。如果一个对象没有响应消息，Ruby会发送一条带有消息选择器的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", :some_other_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，如果您定义method_missing，则还应相应地定义respond_to_missing?。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

Answer 2

class X
  def method_missing(sym,*args)
    puts "Method #{sym} called with #{args}"
  end
end
a = X.new
a.blah("hello","world")

#=> Method blah called with ["hello", "world"]

Answer 3

IIRC，你可以在ruby类中定义method_missing来处理这个问题。很抱歉，我无法提供具体信息。

Answer 4

class Test
  def say
     puts "hi"
  end
end

你可以通过

调用say方法

obj = Test.new
obj.send "say"

并使用

检查方法可用性

obj.respond_to? "say"

最后，整理所有

if (obj.respond_to? "say")
  obj.send "say"
end

让ruby对象响应任意消息？

4 个答案: