Question

我正在尝试了解在this blog post发布的mixins的代码。

这些mixins在mixins中调用来自login_required的{{1}}装饰器，但它们由来自django.contrib.auth.decorators的{{1}}装饰。在下面的示例代码中，我不明白为什么我需要装饰method_decorator装饰器。

django.utils.decorators

login_required装饰器说它用于“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，我也可以使用装饰器。

我的装饰师

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)

我的类直接调用上面的装饰器会产生与调用method_decorator

装饰的装饰器相同的结果

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

Answer 1

Django的method_decorator设置为正确地将self参数传递给修饰函数。您在上面使用run_eight_times装饰器编写的测试用例中没有显示的原因是inner_func中的run_eight_times通过*args盲目地将所有参数传递给myfunc和**kwargs。一般来说，情况并非如此。

要通过示例查看此内容，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的视图装饰器将返回一个带有签名(request, *args, **kwargs)的函数。对于基于类的视图，这应该是(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。

为什么我需要使用@method_decorator来装饰login_required装饰器

1 个答案: