flask 中xx.init_app(app)方法

bootstrap = Bootstrap() 
mail = Mail() 
moment = Moment() 
db = SQLAlchemy() 

def create_app(config_name): 
app = Flask(__name__) 

#将指定的配置通过from_object()方法导入app.config字典配置对象 

app.config.from_object(config[config_name]) 

config[config_name].init_app(app) 

bootstrap.init_app(app) 
mail.init_app(app) 
moment.init_app(app) 
db.init_app(app) 

http://flask.pocoo.org/docs/0.12/patterns/appfactories/ 
flask 文档关于工厂模式里面提到了上面的这种套路。 

It ’ s preferable to create your extensions and app factories so that the extension object does not initially get bound to the application. 

Using Flask-SQLAlchemy, as an example, you should not do something along those lines: 

def create_app(config_filename): 
app = Flask(__name__) 
app.config.from_pyfile(config_filename) 

db = SQLAlchemy(app) 

But, rather, in model.py (or equivalent): 

db = SQLAlchemy() 

and in your application.py (or equivalent): 

def create_app(config_filename): 
app = Flask(__name__) 
app.config.from_pyfile(config_filename) 

from yourapplication.model import db 
db.init_app(app)