django-cms 代码研究（八）app hooks

app钩子，啥玩意呢？就是把现有的app，集成到cms的一种手段。有两种实现方式：1) 定义cms_app.py，如下：

from cms.app_base import CMSApp
from cms.apphook_pool import apphook_pool
from django.utils.translation import ugettext_lazy as _

class MyApphook(CMSApp):
name = _("My Apphook")
urls = ["myapp.urls"]

apphook_pool.register(MyApphook)

官方文档查看这里：http://docs.django-cms.org/en/latest/extending_cms/app_integration.html#app-hooks加载逻辑，通过discover_apps的load('cms_app')来加载(前提是在settings.py中未定义 CMS_APPHOOKS):在所有的installed_app中，查找cms_app模块，并自动import_module2) 在setting.py中定义CMS_APPHOOKS

APPHOOKS=(
'yourmodule.you_object1','yourmodule.you_object2',...
)

这是从源码中分析的来的，如下：C:\Python27\Lib\site-packages\django_cms-3.0.3-py2.7.egg\cms\apphook_pool.py (45~57)

def discover_apps(self):
self.apphooks = get_cms_setting('APPHOOKS')

if self.apphooks:
for cls in iterload_objects(self.apphooks):
try:
self.register(cls, discovering_apps=True)
except AppAlreadyRegistered:
pass

else:
load('cms_app')

self.discovered = True

iterload_objects,是一个生成器，如下：

def iterload_objects(import_paths):
"""
Load a list of objects.
"""
for import_path in import_paths:
yield load_object(import_path)

load_object

def load_object(import_path):
if '.' not in import_path:
raise TypeError(
"'import_path' argument to 'django_load.core.load_object' must "
"contain at least one dot."
)
module_name, object_name = import_path.rsplit('.', 1)
module = import_module(module_name)
return getattr(module, object_name)

顺便分析下　C:\Python27\Lib\site-packages\django_cms-3.0.3-py2.7.egg\cms\apphook_pool.py的源码：实例变量：

def __init__(self):
self.apphooks = []
self.apps = {}
self.discovered = False

方法：clear/register/discover_apps/get_apphooks/get_apphook其中： discover_apps上面已经分析过了。clear，清空实例变量，如下（作者说，python不需要clear，会自动回收，这个方法该砍掉了）：

def clear(self):
# TODO: remove this method, it's Python, we don't need it.
self.apphooks = []
self.apps = {}
self.discovered = False

register，用于注册app，app的基类如下：

class CMSApp(object):
name = None
urls = None
menus = []
app_name = None
permissions = True

register，本质是把app放到apphook_pool实例的apps中，不过之前会有一些验证，如下：

def register(self, app, discovering_apps=False):
if self.apphooks and not discovering_apps:
return

if app.__name__ in self.apps:
raise AppAlreadyRegistered(
'A CMS application %r is already registered' % app.__name__)

if not issubclass(app, CMSApp):
raise ImproperlyConfigured(
'CMS application must inherit from cms.app_base.CMSApp, '
'but %r does not' % app.__name__)

if not hasattr(app, 'menus') and hasattr(app, 'menu'):
warnings.warn("You define a 'menu' attribute on CMS application %r, "
"but the 'menus' attribute is empty, did you make a typo?" % app.__name__)

self.apps[app.__name__] = app

其干活的代码只有最后一句：

self.apps[app.__name__] = app

get_apphooks， 返回一个列表 [(app,app.name)....],并按照app.name排序，如下：

def get_apphooks(self):
hooks = []

if not self.discovered:
self.discover_apps()

for app_name in self.apps:
app = self.apps[app_name]

if app.urls:
hooks.append((app_name, app.name))

# Unfortunately, we loose the ordering since we now have a list of tuples. Let's reorder by app_name:
hooks = sorted(hooks, key=lambda hook: hook[1])

return hooks

get_apphook,根据app名字查找app，代码如下：

def get_apphook(self, app_name):
if not self.discovered:
self.discover_apps()

try:
return self.apps[app_name]
except KeyError:
# deprecated: return apphooks registered in db with urlconf name instead of apphook class name
for app in self.apps.values():
if app_name in app.urls:
return app

raise ImproperlyConfigured('No registered apphook %r found' % app_name)