django - 为什么需要用@method_decorator装饰login_required装饰器

Question

我正在尝试了解this blog post上发布的mixins的代码。

这些mixins从mixins中的login_required调用django.contrib.auth.decorators装饰器，但它们通过method_decorator中的django.utils.decorators装饰。
在下面的示例代码中，我不明白为什么需要装饰login_required装饰器。

from django.utils.decorators import method_decorator
from django.contrib.auth.decorators import login_required
class LoginRequiredMixin(object):
    """
    View mixin which verifies that the user has authenticated.

    NOTE:
        This should be the left-most mixin of a view.
    """
    # Why do I need to decorate login_required here
    @method_decorator(login_required)
    def dispatch(self, *args, **kwargs):
        return super(LoginRequiredMixin, self).dispatch(*args, **kwargs) 

method_decorator装饰器表示它用于“将函数装饰器转换为方法装饰器”，但是在测试代码中，即使没有method_decorator，我也可以使用我的装饰器。

我的装饰

def run_eight_times(myfunc):
    def inner_func(*args, **kwargs):
        for i in range(8):
            myfunc(*args, **kwargs)
    return inner_func 

我的调用上述装饰器的类直接产生与调用 method_decorator装饰的装饰器相同的结果

from django.utils.decorators import method_decorator
class Myclass(object):

    def __init__(self,name,favorite_dish):
        self.name = name
        self.favorite_dish = favorite_dish

    # This next line is not required
    #@method_decorator(run_eight_times)
    @run_eight_times
    def undecorated_function(self):
        print "%s likes spam in his favorite dish %s" % (self.name,self.favorite_dish) 

Answer 1

Django的method_decorator设置为将self参数正确传递给装饰函数。在您上面用run_eight_times装饰器编写的测试用例中未显示出来的原因是，inner_func中的run_eight_times盲目地通过*args和**kwargs将所有参数传递给myfunc。通常，情况并非如此。

要在您的示例中看到它，请尝试以下操作:

from django.utils.decorators import method_decorator

def run_eight_times(myfunc):
    def inner_func(what_he_likes, **kwargs):
        # override...
        what_he_likes = 'pizza'
        for i in range(8):
            myfunc(what_he_likes, **kwargs)
    return inner_func

class MyClass(object):

    def __init__(self, name, favorite_dish):
        self.name = name
        self.favorite_dish = favorite_dish

    # This next line required!
    @method_decorator(run_eight_times)
    #@run_eight_times
    def undecorated_function(self, what_he_likes):
        print "%s likes %s in his favorite dish %s" % (
            self.name, what_he_likes, self.favorite_dish
        )

def main():
    inst = MyClass('bob', 'burrito')
    inst.undecorated_function('hammy spam')

if __name__ == '__main__':
    main()

具体来说，Django的 View 装饰器将返回带有签名 (request, *args, **kwargs)的函数。对于基于类的 View ，应为 (self, request, *args, **kwargs)。这就是 method_decorator所做的-将第一个签名转换为第二个签名。