django - 未调用 mixin 中的 get_context_data

Question

我是 Django 的新手。我想使用 mixin 将一些数据返回到多个基于类的 View 。我在 mixin 中定义的 get_context_data 似乎没有在 View 类中调用。

class MyMixin(object):
    def get_context_data(self, *args, **kwargs):
        data = super(MyMixin, self).get_context_data(*args, **kwargs)
        from django.utils import timezone
        data['object'].now = timezone.now()
        return data

class PageDetail(DetailView, MyMixin):
    model = MyModel
    template_name = 'page-detail.html'

    def get_context_data(self, *args, **kwargs):
        data = super(PageDetail, self).get_context_data(*args, **kwargs)
        return data

Answer 1

您以错误的顺序定义基类:

class PageDetail(<b><s>DetailView, MyMixin</s></b>):
    # ...

表示method resolution order (MRO)定义为:

>>> PageDetail.__mro__
(<class 'PageDetail'>,
 <class 'django.views.generic.detail.DetailView'>,
 <class 'django.views.generic.detail.SingleObjectTemplateResponseMixin'>,
 <class 'django.views.generic.base.TemplateResponseMixin'>,
 <class 'django.views.generic.detail.BaseDetailView'>,
 <class 'django.views.generic.detail.SingleObjectMixin'>,
 <class 'django.views.generic.base.ContextMixin'>,
 <class 'django.views.generic.base.View'>,
 <class 'MyMixin'>,
 <class 'object'>)

这意味着如果我们遵循 super(PageDetail, self).get_context_data(*args, **kwargs)，这将永远到达MyMixin ，因为 ContextMixin 将其定义为:

class ContextMixin:

    def get_context_data(self, **kwargs):
        if 'view' not in kwargs:
            kwargs['view'] = self
        if self.extra_context is not None:
            kwargs.update(self.extra_context)
        return kwargs

因此不调用任何super()方法。

您应该将 PageDetail 定义为:

class PageDetail(<b>MyMixin, DetailView</b>):
    # ...

所以现在 MRO 定义为:

>>> PageDetail.__mro__
(<class 'PageDetail'>,
 <class 'MyMixin'>,
 <class 'django.views.generic.detail.DetailView'>,
 <class 'django.views.generic.detail.SingleObjectTemplateResponseMixin'>,
 <class 'django.views.generic.base.TemplateResponseMixin'>,
 <class 'django.views.generic.detail.BaseDetailView'>,
 <class 'django.views.generic.detail.SingleObjectMixin'>,
 <class 'django.views.generic.base.ContextMixin'>,
 <class 'django.views.generic.base.View'>,
 <class 'object'>)

因此 super(PageDetail, self).get_context_data(*args, **kwargs) 将调用 MyMixin 的 get_context_data类，然后它将调用 MRO 中的 next 方法。