Function_Class_Based_view两种视图

什么时候用 FBV 或者 CBV

流程图:

通常情况下使用 CBV， FBV用来补充

FBVs to implement 
    only the custom error views 
or 
    complicated ones that would be a pain to implement with CBVs.

不要把视图逻辑(View Logic)放在 URLlConfs 中

参考 Django’s URL design philosophy

1 The views modules should contain view logic.

2 The URL modules should contain URL logic.

一个不好的实例 (虽然是官方实例)

# Don't do this!
from django.conf.urls import url
from django.views.generic import DetailView
from tastings.models import Tasting

urlpatterns = [
    url(r'^(?P<pk>\d+)/$',
    DetailView.as_view(
    model=Tasting,
    template_name='tastings/detail.html'),
    name='detail'),
    
    url(r'^(?P<pk>\d+)/results/$',
    DetailView.as_view(
    model=Tasting,
    template_name='tastings/results.html'),
    name='results'),
]

缺点

Loose coupling
1  耦合性太强(model 和 view在一起, 无法重用 view)

Infinite flexibility
2  缺少灵活性

推荐的写法

# app tastings

# tastings/views.py

from django.urls import reverse
from django.views.generic import ListView, DetailView, UpdateView
from .models import Tasting

class TasteListView(ListView):
    model = Tasting
    
    
class TasteDetailView(DetailView):
    model = Tasting
    
    
class TasteResultsView(TasteDetailView):
    template_name = 'tastings/results.html'
    
    
class TasteUpdateView(UpdateView):
    model = Tasting
    
    def get_success_url(self):
        return reverse('tastings:detail',
            kwargs={'pk': self.object.pk})
            

#  tastings/urls.py

from . import views

urlpatterns = [
    url(
        regex=r'^$',
        view=views.TasteListView.as_view(),
        name='list'
    ),
    url(
         regex=r'^(?P<pk>\d+)/$',
         view=views.TasteDetailView.as_view(),
         name='detail'
     ),
     url(
         regex=r'^(?P<pk>\d+)/results/$',
         view=views.TasteResultsView.as_view(),
         name='results'
     ),
     url(
         regex=r'^(?P<pk>\d+)/update/$',
         view=views.TasteUpdateView.as_view(),
         name='update'
     )
 ]
   

使用 URL Namespace

在项目根目录下 urls.py

urlpatterns += [
    url(r'^tastings/', include('tastings.urls', namespace='tastings')),
]

在 app tastings 中就可以使用 namespace

# tastings/views.py snippet

class TasteUpdateView(UpdateView):
    model = Tasting
    
    def get_success_url(self):
    
        return reverse('tastings:detail',
                  kwargs={'pk': self.object.pk})


# taste_list.html

{  extends 'base.html'  }
{  block title  }Tastings{  endblock title  }
{   block content  }
<ul>
{   for taste in tastings  }
<li>
<a href="{  url 'tastings:detail' taste.pk  }"></a>
<small>
(<a href="{  url 'tastings:update' taste.pk  }">update</a>)
</small>
</li>
{  endfor  }
</ul>
{  endblock content  }

Django 的 views 是函数

Django的views实际是接收(HTTP request object)的函数， 然后返回HTTP response object

# Django FBV as a function
HttpResponse = view(HttpRequest)

# Deciphered into basic math (remember functions from algebra?)
y = f(x)

# ... and then translated into a CBV example
HttpResponse = View.as_view()(HttpRequest)

• 最简单的视图

# The simplest FBV
def simplest_view(request):
    # Business logic goes here
    return HttpResponse('FBV')
    
    
# The simplest CBV
class SimplestView(View):
    def get(self, request, *args, **kwargs):
    # Business logic goes here
    return HttpResponse('CBV')

不要在views中使用 locals()

# date
def ice_cream_store_display(request, store_id):
    store = get_object_or_404(Store, id=store_id)
    date = timezone.now()
    return render(request, 'melted_ice_cream_report.html', locals())

# now
def ice_cream_store_display(request, store_id):
    store = get_object_or_404(Store, id=store_id)
    now = timezone.now()
    return render(request, 'melted_ice_cream_report.html', locals())

# 这里的now与函数now命名冲突

正确的写法

def ice_cream_store_display(request, store_id):
    return render(
        request,
        'melted_ice_cream_report.html',
        {
            'store': get_object_or_404(Store, id=store_id),
            'now': timezone.now()
         }
    )