[django]编写作用于视图（view）的装饰器（Decorator）

本文假设读者已经知道如何编写基本的装饰器代码，否则请自行 google：“python 装饰器”and/or “python decorator”。

不带参数的装饰器

from functools import wraps


def object_does_not_exist(func):
    @wraps(func)
    def returned_wrapper(request, *args, **kwargs):
        try:
            return func(request, *args, **kwargs)
        except ObjectDoesNotExist:
            raise Http404()
    return returned_wrapper

用法：

@object_does_not_exist
def detail(request):
    pass

带参数的装饰器

  • 第一种写法：

    def object_does_not_exist(redirect=None):
    def decorator(func):
        @wraps(func)
        def returned_wrapper(request, *args, **kwargs):
            try:
                return func(request, *args, **kwargs)
            except ObjectDoesNotExist:
                if redirect:
                    return HttpResponseRedirect(redirect)
                else:
                    raise Http404()
        return returned_wrapper
    return decorator

    用法：

    @object_does_not_exist(redirect='/')
def detail(request):
    pass

# 记得加个闭合括号，否则会出现类似 takes exactly 1 argument (0 given) 的错误
@object_does_not_exist()
def foo(request):
    pass

  • 第二种写法：

    def object_does_not_exist(func=None, redirect=None):
    def decorator(func):
        @wraps(func)
        def returned_wrapper(request, *args, **kwargs):
            try:
                return func(request, *args, **kwargs)
            except ObjectDoesNotExist:
                if redirect:
                    return HttpResponseRedirect(redirect)
                else:
                    raise Http404()
        return returned_wrapper

    if not func:
        def foo(func):
            return decorator(func)
        return foo

    else:
        return decorator(func)

    用法：

    @object_does_not_exist(redirect='/')
def detail(request):
    pass

@object_does_not_exist
def foo(request):
    pass

第二种方法可以解决 got an unexpected keyword argument 错误。

参考

Comments