Django's routing system: URL

A, URLconf configuration

The basic format
```
from django.conf.urls import url
urlpatterns = [
     url(正则表达式, views视图，参数，别名),
]
```
- Parameter Description
  - Regular Expressions: A regular expression string
  - views view: a callable object, a view is generally a function of
  - Parameters: The optional parameters to be passed to the default view function (a dictionary)
  - Alias: An optional parameter name

django 2.0 version of the routing system

Re_path version 2.0 and version 1.11 of the url is the same usage

from django.urls import path，re_path
urlpatterns = [
    path('articles/2003/', views.special_case_2003),
]

Second, the regular expression

basic configuration

from django.conf.urls import url
from . import views
urlpatterns = [
    url(r'^articles/2003/$', views.special_case_2003),
]

Precautions
- urlpatterns the elements one by one in the writing order to match the regular expression from the top down, will not continue once the match is successful
- To capture a value from the URL, only to place a pair of parentheses around it (using the packet match)
- No need to add a leading backslash, because each URL has. For example, it should be ^ articles, not ^ / articles
- Each regular expression in front of the 'r' is optional, but suggested adding
Supplement
- Whether open access URL address is not behind / jump to the path with / of configuration items: APPEND_SLASH = True
- Django settings.py file in the default configuration does not APPEND_SLASH this parameter, but Django default this parameter is APPEND_SLASH = True, its role is automatically added to the end of the URL '/'

Third, the group name to match

Group: simple regular expression matching packet (by the parentheses) to capture the value of the URL and passed as parameters to the position of the view function

from django.conf.urls import url
from . import views
urlpatterns = [
    url(r'^articles/([0-9]{4})/$', views.year_archive),
    url(r'^articles/([0-9]{4})/([0-9]{2})/$', views.month_archive),
]

Naming packet: packet using regular expression matching name set to capture the value of the URL and passed as parameters to the view of the function key
```
from django.conf.urls import url
from . import views
urlpatterns = [
    url(r'^articles/(?P<year>[0-9]{4})/$', views.year_archive),
    url(r'^articles/(?P<year>[0-9]{4})/(?P<month>[0-9]{2})/$', views.month_archive),
]
```
- Added: When the third parameter url of a dictionary representing additional keyword arguments you want to pass to the view function
  - When the dictionary to pass additional parameters in the URL parameters and capture the value of the named keyword arguments of the same name, the function is called, it will use a dictionary of parameters, rather than captured parameters in the URL
  - That is the priority: Additional parameters> URL capture parameters
UPLconf match Location:
- URLconf look at the URL request, it will be treated as a normal Python string, not including GET and POST parameters, and domain name
  - http://www.example.com/myapp/Request, URLconf will look for / myapp /
  - http://www.example.com/myapp/?page=3Request, URLconf will look for / myapp /
- URLconf request method does not check, i.e., all requests method (with one URL POST, GET, HEAD, etc.), are routed to the same function
Capturing parameters are strings: each captured in a URLconf parameters as a normal Python string to view function, regardless of regular expressions to match what way

There are individual cases, need to specify a default value view function

# urls.py中
from django.conf.urls import url
from . import views
urlpatterns = [
    url(r'^blog/$', views.page),
    url(r'^blog/page(?P<num>[0-9]+)/$', views.page),
]
# 两个URL模式指向相同的view,但是第一个模式并没有从URL中捕获任何东西

# views.py中，可以为num指定默认值
def page(request, num="1"):
    pass
# 如果第一个模式匹配上了，page函数将使用其默认参数num=“1”,如果第二个模式匹配，page将使用正则表达式捕获到的num值

include: route distribution

According to different functions or types, you can put different routing functions written in the function of the app file, include the use of linked url equivalent to the different functions in different space

from django.conf.urls import include, url
urlpatterns = [
   url(r'^admin/', admin.site.urls),
   url(r'^app01/', include('app01.urls')),  # 可以包含其他的URLconfs文件
]

Supplementary: app01.urls

from django.conf.urls import url
from . import views
urlpatterns = [
    url(r'^blog/$', views.blog),
    url(r'^blog/(?P<year>[0-9]{4})/(?P<month>\d{2})/$', views.blogs),
]

include a namespace parameters: namespace
- Easy to distinguish different routing functions with the same name present in the space, to facilitate exact function specified

from django.conf.urls import include, url
urlpatterns = [
    url(r'^app01/', include('app01.urls', namespace='app01')),
    url(r'^app02/', include('app02.urls', namespace='app02')),
]

Fourth, the name and URL of the reverse analysis

4.1 URL name

Url fourth parameter is an alias, i.e. an optional parameter name

Named: name = 'alias'

from django.conf.urls import url
urlpatterns = [
 url(r'^home', views.home, name='home'),        # 给我的url匹配模式起名为 home
 url(r'^index/(\d*)', views.index, name='index'),       # 给我的url匹配模式起名为index
]

4.2 reverse lookup

Reverse resolution: get the full URL path alias

Case 1: Static Routing

name

from django.conf.urls import url
urlpatterns = [
 url(r'^blog/$', views.blog, name='blog'),
]

Used in the template

{% url 'blog' %}         {# 完整URL路径：/blog/ #}

py file in use

from django.urls import reverse
reverse('blog')           # 完整URL路径：/blog/

Scenario 2: Grouping

name

from django.conf.urls import url
urlpatterns = [
 url(r'^blog/([0-9]{4})/(\d{2})/$', views.blogs, name='blogs'),
]

Used in the template

{% url 'blogs' 2222 12 %}        {# 完整URL路径：/blog/2222/12/ #}

py file in use

from django.urls import reverse
reverse('blogs',args=('2019','06'))        # 完整URL路径：/blog/2019/06/

Case three: group name

name

from django.conf.urls import url
urlpatterns = [
 url(r'^blog/(?P<year>[0-9]{4})/(?P<month>\d{2})$', views.blogs, name='blogs'),
]

Used in the template

{% url 'blogs' year=2222 month=12 %}      {# 完整URL路径：/blog/2222/12/ #}

py file in use

from django.urls import reverse
reverse('blogs',kwargs={'year':'2019','month':'06'})      # 完整URL路径：/blog/2019/06/

Fifth, reverse analysis of a namespace mode

urls.py in the project directory

from django.conf.urls import url, include
urlpatterns = [
    url(r'^app01/', include('app01.urls', namespace='app01')),
    url(r'^app02/', include('app02.urls', namespace='app02')),
]

app01 in urls.py

from django.conf.urls import url
from app01 import views
urlpatterns = [
    url(r'^(?P<pk>\d+)/$', views.detail, name='detail')
]

app02 in urls.py

from django.conf.urls import url
from app02 import views
urlpatterns = [
    url(r'^(?P<pk>\d+)/$', views.detail, name='detail')
]

Reverse lookup syntax: 'namespace name: URL name'

Use in the template

{% url 'app01:detail' pk=12 %}
{% url 'app02:detail' pk=12 %}

Use the py file

from django.urls import reverse
reverse('app01:detail', kwargs={'pk':11})
reverse('app01:detail', kwargs={'pk':11})

Note: If you have a multi-layer route distribution, with multiple namespace name, the namespace name should be preceded by an alias layer by layer
```
{# 简单示例：app01是第一层路由空间的namespace，xxx是第二层路由空间的namespace #}
{% url 'app01:xxx:index' %}
```