如何在Django中编写自己的装饰器？

Question

我的models.py文件如下：

from django.contrib.auth.models import User

class Shopkeeper(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE, primary_key=True)
    # ...


class Customer(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE, primary_key=True)
# ...

我有一些视图，只有客户登录后才能访问，而店主则不能。 反之亦然。 如何为此类任务编写装饰器？

Answer 1

装饰器没有什么神奇的东西，它是一个将要装饰的函数（或类）作为输入并对其进行一些更改的函数。 如果我们查看login_required装饰器[GitHub] ， login_required看到：

 def login_required(function=None, redirect_field_name=REDIRECT_FIELD_NAME, login_url=None): """ Decorator for views that checks that the user is logged in, redirecting to the log-in page if necessary. """ actual_decorator = user_passes_test( lambda u: u.is_authenticated, login_url=login_url, redirect_field_name=redirect_field_name ) if function: return actual_decorator(function) return actual_decorator 

因此，我们实际上可以简单地对user_passes_test装饰器进行特殊处理：

from django.contrib.auth.decorators import user_passes_test

def shopkeeper_required(function=None):
    def is_shopkeeper(u):
        return Shopkeeper.objects.filter(user=u).exists()
    actual_decorator = user_passes_test(is_shopkeeper)
    if function:
        return actual_decorator(function)
    else:
        return actual_decorator

def customer_required(function=None):
    def is_customer(u):
        return Customer.objects.filter(user=u).exists()
    actual_decorator = user_passes_test(is_customer)
    if function:
        return actual_decorator(function)
    else:
        return actual_decorator

然后，您可以例如将其实现为：

@login_required
@shopkeeper_required
def some_shopkeeper_view(request):
    # ...
    pass

@login_required
@customer_required
def some_customer_view(request):
    # ...
    pass

请注意，尽管在很多情况下，此@shopkeeper_required并不会真正强制用户登录。

编辑 ：

我们可以将其与@login_required合并（通过添加一个用作开关以默认打开或关闭此行为的参数），例如：

from django.contrib.auth.decorators import user_passes_test

def shopkeeper_required(function=None, login_required=True, redirect_field_name=REDIRECT_FIELD_NAME, login_url=None):
    def is_shopkeeper(u):
        if login_required and not u.is_authenticated: return False
        return Shopkeeper.objects.filter(user=u).exists()
    actual_decorator = user_passes_test(
        is_shopkeeper,
        login_url=login_url,
        redirect_field_name=redirect_field_name
    )
    if function:
        return actual_decorator(function)
    else:
        return actual_decorator

def customer_required(function=None, login_required=True, redirect_field_name=REDIRECT_FIELD_NAME, login_url=None):
    def is_customer(u):
        if login_required and not u.is_authenticated: return False
        return Customer.objects.filter(user=u).exists()
    actual_decorator = user_passes_test(
        is_customer,
        login_url=login_url,
        redirect_field_name=redirect_field_name
    )
    if function:
        return actual_decorator(function)
    else:
        return actual_decorator