Django Admin源码流程

1、总体看Admin执行流程 1. 启动admin

首先须要将django.contrib.admin添加到INSTALL_APP中
     当加载django中app的时候，执行每个app下的admin.py
 2. 注册模型
    每一个模型均可以指定一个ModelAdmin
    封装了该模型特定的管理功能
    实例化一个AdminSite,并告诉它模型类和ModelAmin
    admin.site --> 实例化一个AdminSite
    admin.site.register(Book) 注册Book表
 3.  设计URL并将AdminSite实例挂钩到您的URLconfig中
   url(r'admin/',admin.site.urls)

2、admin.site.register

django启动的时候，顺序为：先register，而后urls分配    
 先看看admin.siter.register作了什么

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首先admin.site = AdminSite()

class AdminSite(object):
    ....

    def __init__(self, name='admin'):
        self._registry = {}   #  AdminSite初始化函数定义了一个字典
        self.name = name
        self._actions = {'delete_selected': actions.delete_selected}
        self._global_actions = self._actions.copy()
        all_sites.add(self)


     def register(self, model_or_iterable, admin_class=None, **options):
        # 判断是否自定义了ModelAdmin
        if not admin_class:
            admin_class = ModelAdmin

        if isinstance(model_or_iterable, ModelBase):
            model_or_iterable = [model_or_iterable]
        for model in model_or_iterable:
            if model._meta.abstract:
                raise ImproperlyConfigured(
                    'The model %s is abstract, so it cannot be registered with admin.' % model.__name__
                )

            if model in self._registry:
                raise AlreadyRegistered('The model %s is already registered' % model.__name__)

            if not model._meta.swapped:

                if options:
                    # For reasons I don't quite understand, without a __module__
                    # the created class appears to "live" in the wrong place,
                    # which causes issues later on.
                    options['__module__'] = __name__
                    admin_class = type("%sAdmin" % model.__name__, (admin_class,), options)

                # 以传入的model类做为字典的key,ModelAdmin做为字典value
                self._registry[model] = admin_class(model, self)

 总结：

　 就是实例化了一个AdminSite类，admin.site 采用的是模板的单例模式

在AdminSite中定义了一个字典
      字典的key是模型类，value是ModelAdmin

3、admin.site.urls

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使用装饰器，将urls()装饰为属性，urls返回的是一个元组，元组的第一个参数是一个列表，由get_urls()返回

@property
def urls(self):
    return self.get_urls(), 'admin', self.name


def get_urls(self):
    from django.conf.urls import url, include
    from django.contrib.contenttypes import views as contenttype_views

    def wrap(view, cacheable=False):
        .....
        return update_wrapper(wrapper, view)

    # Admin-site-wide views.
    urlpatterns = [
        url(r'^$', wrap(self.index), name='index'),
        url(r'^login/$', self.login, name='login'),
        url(r'^logout/$', wrap(self.logout), name='logout'),
        url(r'^password_change/$', wrap(self.password_change, cacheable=True), name='password_change'),
        url(r'^password_change/done/$', wrap(self.password_change_done, cacheable=True),
            name='password_change_done'),
        url(r'^jsi18n/$', wrap(self.i18n_javascript, cacheable=True), name='jsi18n'),
        url(r'^r/(?P<content_type_id>\d+)/(?P<object_id>.+)/$', wrap(contenttype_views.shortcut),
            name='view_on_site'),
    ]

    valid_app_labels = []
    #   模型类,ModelAdmin     self._registry字典
    for model, model_admin in self._registry.items():
        urlpatterns += [
            # url(r'^%s/%s/' % (模型所在的app名, 模型名), include(每一个模型对应的ModelAdmin中urls)),
            url(r'^%s/%s/' % (model._meta.app_label, model._meta.model_name), include(model_admin.urls)),
        ]
        if model._meta.app_label not in valid_app_labels:
            valid_app_labels.append(model._meta.app_label)
        .....

    #返回了n个URL
    return urlpatterns

首先urls是一个函数，被装饰为属性，urls返回一个元组，元组的第一个参数是列表，由get_urls()返回。
在get_urls()中定义了一个urlpatterns,并最终返回，urlpatterns里面存放的是url匹配规则和对应的视图函数。
当用户在admin中注册模型类的时候：

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admin.site.register(models.UserInfo)　# 注册的时候没有传入admin_class,默认使用的是ModelAdmin　

会根据下面的代码添加到urlpatterns中

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for model, model_admin in self._registry.items():

urlpatterns += [
    url(r'^%s/%s/' % (model._meta.app_label, model._meta.model_name), include(model_admin.urls)),
]
  model._meta.app_label: 是model类存在的app名，就是UserInfo存在哪一个app中      model._mate.model_name:是模型类的类名，小写。这里是userinfo。
  这样就生成了/app01/userinfo/ 这样的url前缀。
  include(model_admin.urls)：包含模型类对应ModelAdmin中urls。这里没有指定ModelAdmin，因此使用官方默认的ModelAdmin

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4、ModelAdmin.urls
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def get_urls(self):

from django.conf.urls import url

    def wrap(view):
        def wrapper(*args, **kwargs):
            return self.admin_site.admin_view(view)(*args, **kwargs)
        wrapper.model_admin = self
        return update_wrapper(wrapper, view)

    info = self.model._meta.app_label, self.model._meta.model_name

    urlpatterns = [
        url(r'^$', wrap(self.changelist_view), name='%s_%s_changelist' % info),
        url(r'^add/$', wrap(self.add_view), name='%s_%s_add' % info),
        url(r'^(.+)/history/$', wrap(self.history_view), name='%s_%s_history' % info),
        url(r'^(.+)/delete/$', wrap(self.delete_view), name='%s_%s_delete' % info),
        url(r'^(.+)/change/$', wrap(self.change_view), name='%s_%s_change' % info),
        # For backwards compatibility (was the change url before 1.9)
        url(r'^(.+)/$', wrap(RedirectView.as_view(
            pattern_name='%s:%s_%s_change' % ((self.admin_site.name,) + info)
        ))),
    ]
    return urlpatterns

@property
def urls(self):
    return self.get_urls()

在ModelAdmin中urls()也是一个函数，被装饰器装饰为属性。get_urls()返回一个urlpatterns.
红色部分的urlpatterns 代表了django admin为何注册了一个类以后就为这个类提供了基本的增删改查等基本的url和映射了。

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[size=1.5em]5、最终的url

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