# 路由

# 路由匹配

from django.urls import path

from . import views

urlpatterns = [
    path('articles/2003/', views.special_case_2003),
    path('articles/<int:year>/', views.year_archive),
    path('articles/<int:year>/<int:month>/', views.month_archive),
    path('articles/<int:year>/<int:month>/<slug:slug>/', views.article_detail),
]

articles/<int:year>/year为路径参数，int为转换器，不需要/articles，因为每个url都有

路径匹配不包含domain，query_parameters，method，比如

https://www.example.com/myapp/?page=3只匹配myapp/部分，注意myapp后面的/也纳入匹配

urlpatterns为规定变量，必须是path()或re_path()序列

# 路径参数格式

str: 默认，匹配除路径分隔符'/'之外的字符串
int：匹配0和正整数
slug：以连字符或下划线连接的ASCII 字符或数字
uuid：连字符连接的小写ASCII字符或数字，返回UUID实例
path：任何非空字符串，包括路径分隔符'/'

# 自定义格式转换器

# 定义converter

一个converter是一个类，包括以下几个要点：

class FourDigitYearConverter:
    regex = '[0-9]{4}'

    def to_python(self, value):
        return int(value)

    def to_url(self, value):
        return '%04d' % value

regex类属性
to_python方法
to_url方法

# 通过register_converter()注册

from django.urls import path, register_converter

from . import converters, views

register_converter(converters.FourDigitYearConverter, 'yyyy')

urlpatterns = [
    path('articles/2003/', views.special_case_2003),
    path('articles/<yyyy:year>/', views.year_archive),
    ...
]

# 使用正则表达式re_path()

# 命名分组

from django.urls import path, re_path

from . import views

urlpatterns = [
    path('articles/2003/', views.special_case_2003),
    re_path(r'^articles/(?P<year>[0-9]{4})/$', views.year_archive),
    re_path(r'^articles/(?P<year>[0-9]{4})/(?P<month>[0-9]{2})/$', views.month_archive),
    re_path(r'^articles/(?P<year>[0-9]{4})/(?P<month>[0-9]{2})/(?P<slug>[\w-]+)/$', views.article_detail),
]

格式(?P<name>pattern)

pattern将作为str传递给name

# 嵌套参数

from django.urls import re_path

urlpatterns = [
    re_path(r'^blog/(page-(\d+)/)?$', blog_articles),                  # bad
    re_path(r'^comments/(?:page-(?P<page_number>\d+)/)?$', comments),  # good
]

?:page-(?P<page_number>\d+)捕获page_number参数，不捕获page-xxx

# 指定默认参数

# URLconf
from django.urls import path

from . import views

urlpatterns = [
    path('blog/', views.page),
    path('blog/page<int:num>/', views.page),
]

# View (in blog/views.py)
def page(request, num=1):
    # Output the appropriate page of blog entries, according to num.
    ...

当匹配第一个路由时，num使用默认值

# 错误处理

当匹配不到路由或程序出现异常，Django自动触发异常处理视图

错误处理必须配置在 root URLconf中，通过4个变量指定：

handler400 = 'mysite.views.my_custom_bad_request_view'
handler403 = 'mysite.views.my_custom_permission_denied_view'
handler404 = 'mysite.views.my_custom_page_not_found_view'
handler500 = 'mysite.views.my_custom_error_view'

默认配置

handler400 = 'django.views.defaults.bad_request'
handler403 = 'django.views.defaults.permission_denied'
handler404 = 'django.views.defaults.page_not_found'
handler500 = 'django.views.defaults.server_error'

# 嵌套路由

from django.urls import include, path

urlpatterns = [
    # ... snip ...
    path('community/', include('aggregator.urls')),
    path('contact/', include('contact.urls')),
    # ... snip ...
]

include后面可以是一个模块，模块内有urlpatterns属性，也可以是一个list或者tuple。

# 路径参数向下传递

# In settings/urls/main.py
from django.urls import include, path

urlpatterns = [
    path('<username>/blog/', include('foo.urls.blog')),
]

# In foo/urls/blog.py
from django.urls import path
from . import views

urlpatterns = [
    path('', views.blog.index),
    path('archive/', views.blog.archive),
]

username将向下传递到included URLconf

# 传递额外参数

from django.urls import path
from . import views

urlpatterns = [
    path('blog/<int:year>/', views.year_archive, {'foo': 'bar'}),
]

当请求 /blog/2005/时，django会访问views.year_archive(request, year=2005, foo='bar')

如果路径参数和额外参数发生了冲突，则取额外参数

# 额外参数向下传递

# main.py
from django.urls import include, path

urlpatterns = [
    path('blog/', include('inner'), {'blog_id': 3}),
]

# inner.py
from django.urls import path
from mysite import views

urlpatterns = [
    path('archive/', views.archive),
    path('about/', views.about),
]

同路径参数一样，额外参数也会向下传递

# 路由别名

为了防止模板或代码中对url进行硬编码，django支持为每个url提供一个别名。

from django.urls import path

from . import views

urlpatterns = [
    #...
    path('articles/<int:year>/', views.year_archive, name='news-year-archive'),
    #...
]

name='news-year-archive'即为别名

<a href="{% url 'news-year-archive' 2012 %}">2012 Archive</a>
{# Or with the year in a template context variable: #}
<ul>
{% for yearvar in year_list %}
<li><a href="{% url 'news-year-archive' yearvar %}">{{ yearvar }} Archive</a></li>
{% endfor %}
</ul>

在template中使用url 模板tag解析别名

from django.http import HttpResponseRedirect
from django.urls import reverse

def redirect_to_year(request):
    # ...
    year = 2006
    # ...
    return HttpResponseRedirect(reverse('news-year-archive', args=(year,)))

在代码中使用reverse方法解析别名

# 命名空间

由于不同的应用可能使用相同的路由别名，为了防止冲突，需要给不同的include添加命名空间。

命名空间分为两种：

实例命名空间

from django.urls import include, path

urlpatterns = [
    path('author-polls/', include('polls.urls', namespace='author-polls')),
    path('publisher-polls/', include('polls.urls', namespace='publisher-polls')),
]

在include中指定

应用命名空间

from django.urls import path

from . import views

app_name = 'polls'
urlpatterns = [
    path('', views.IndexView.as_view(), name='index'),
    path('<int:pk>/', views.DetailView.as_view(), name='detail'),
    ...
]

使用app_name变量指定

django会优先使用instance namespace，如果没有则使用application namespace。

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