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 CMSAppfrom cms.apphook_pool import apphook_poolfrom 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_module
2) 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)