python的callback函数原理

"""
class C(object):
    a = ‘abc‘
    def __getattribute__(self, *args, **kwargs):
        print("__getattribute__() is called")
        print args
        if args[0] == ‘a‘:
            return object.__getattribute__(self, *args, **kwargs)
        else:
            print ‘调用函数foo()‘
            return object.__getattribute__(self,‘foo‘)()
    def foo(self):
        return "hello"
if __name__ == ‘__main__‘:
    c = C()
    print c.foo
"""

class Callback:
    def __init__(self, instance, function_name):
        self.instance = instance # api.self
        self.function_name = function_name # function

    def action(self, params):
        print self.instance.__getattribute__(self.function_name)
        self.instance.__getattribute__(self.function_name)(params)

class Test:
    def __init__(self):
        self.clb = None

    def register(self, clb):
        self.clb = clb # Callback(self, self.function.__name__)

    def do_test(self):
        params = []
        self.clb.action(params)

class Api(object):
    def __init__(self, test_instance):
        test_instance.register(Callback(self, self.function.__name__))

    def function(self, params):
        print params
        print(‘function‘)

t = Test()
a = Api(t)
t.do_test()