flask第一级

#从flask这个包中导入Flask这个类
#Flask这个类是项目的核心，以后很多操作都是基于这个类的对象
#注册url、注册蓝图等都是基于这个类的对象
from flask import Flask

#创建一个Flask对象，传递__name__参数进去
#__name__参数的作用：
#1.可以规定模板和静态文件的查找路劲
#2.以后一些Flask插件，比如Flask-migrate、Flask-SQLAlchemy如果报错了，
#那么Flask可以通过这个参数找到具体的报错位置
app = Flask(__name__)

#@app.route：是一个装饰器
#@app。route（“/”）就是将url中的/映射到hello_world这个视图函数上面
#以后你访问我这个网站的/目录的时候，会执行hello_world这个函数，然后将这个
#返回值返回给浏览器
@app.route('/')
def hello_world():
    return 'Hello World'

if __name__ == '__main__':
    #app.run():Flask中的一个测试应用服务
    # while True: run相当于
    #  listen()
    #  input()
    app.run()

看下 route（‘/’）的源码

先看下一般我们使用装饰器怎么用

无参装饰器

User = None


def decorater(func):
    def wapper(*args,**kwargs):
        if User:
            return func(*args,**kwargs)
        else:
            #就执行相应逻辑
            pass
    return wapper   

有参装饰器

def func(fun,*args,**kwargs):
    def decorater(f):
        def wapper(*args, **kwargs):
            if User:
                return func(*args, **kwargs)
            else:
                # 就执行相应逻辑
                pass
        return wapper
    return decorater

————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————-_
下面看下flask里面是怎么处理的

def route(self, rule, **options):
    """A decorator that is used to register a view function for a
    given URL rule.  This does the same thing as :meth:`add_url_rule`
    but is intended for decorator usage::

        @app.route('/')
        def index():
            return 'Hello World'

    For more information refer to :ref:`url-route-registrations`.

    :param rule: the URL rule as string
    :param endpoint: the endpoint for the registered URL rule.  Flask
                     itself assumes the name of the view function as
                     endpoint
    :param options: the options to be forwarded to the underlying
                    :class:`~werkzeug.routing.Rule` object.  A change
                    to Werkzeug is handling of method options.  methods
                    is a list of methods this rule should be limited
                    to (``GET``, ``POST`` etc.).  By default a rule
                    just listens for ``GET`` (and implicitly ``HEAD``).
                    Starting with Flask 0.6, ``OPTIONS`` is implicitly
                    added and handled by the standard request handling.
    """
    def decorator(f):     #f就是那个注册函数但是这里没有执行
        endpoint = options.pop('endpoint', None)
        self.add_url_rule(rule, endpoint, f, **options) #而是将注册url传入进了 add_url_rule()这个函数,路由规则和注册函数进行绑定
        return f
    return decorator
————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————
看下 add_url_rule

@setupmethod
def add_url_rule(self, rule, endpoint=None, view_func=None,
                 provide_automatic_options=None, **options):
    """Connects a URL rule.  Works exactly like the :meth:`route`
    decorator.  If a view_func is provided it will be registered with the
    endpoint.

    Basically this example::

        @app.route('/')
        def index():
            pass

    Is equivalent to the following::

        def index():
            pass
        app.add_url_rule('/', 'index', index)

    If the view_func is not provided you will need to connect the endpoint
    to a view function like so::

        app.view_functions['index'] = index

    Internally :meth:`route` invokes :meth:`add_url_rule` so if you want
    to customize the behavior via subclassing you only need to change
    this method.

    For more information refer to :ref:`url-route-registrations`.

    .. versionchanged:: 0.2
       `view_func` parameter added.

    .. versionchanged:: 0.6
       ``OPTIONS`` is added automatically as method.

    :param rule: the URL rule as string
    :param endpoint: the endpoint for the registered URL rule.  Flask
                     itself assumes the name of the view function as
                     endpoint
    :param view_func: the function to call when serving a request to the
                      provided endpoint
    :param provide_automatic_options: controls whether the ``OPTIONS``
        method should be added automatically. This can also be controlled
        by setting the ``view_func.provide_automatic_options = False``
        before adding the rule.
    :param options: the options to be forwarded to the underlying
                    :class:`~werkzeug.routing.Rule` object.  A change
                    to Werkzeug is handling of method options.  methods
                    is a list of methods this rule should be limited
                    to (``GET``, ``POST`` etc.).  By default a rule
                    just listens for ``GET`` (and implicitly ``HEAD``).
                    Starting with Flask 0.6, ``OPTIONS`` is implicitly
                    added and handled by the standard request handling.
    """
    if endpoint is None:
        endpoint = _endpoint_from_view_func(view_func)#这个是注册函数的名字
    options['endpoint'] = endpoint #将字典的形式 将函数名字 绑定到 options这个字典上 键值对：
    methods = options.pop('methods', None) #这里用了字典的pop方法，pop（）这个方法有三个参数一个是self就是字典zij，
第二参数就是关键字，第三个就是没有找到这个关键字的默认参数


    # if the methods are not given and the view_func object knows its
    # methods we can use that instead.  If neither exists, we go with
    # a tuple of only ``GET`` as default.
　　

如果没有给出方法，并且view_func对象知道它的方法

方法，我们可以用它来代替。如果两者都不存在，我们就一起去

只有' GET '作为defaul的元组

    if methods is None:
        methods = getattr(view_func, 'methods', None) or ('GET',)#这个用自省中动态的获取里面的方法，methods有值就是直接获取，没有就是None，None就不执行，执行
后面的默认参数元祖
    if isinstance(methods, string_types):#这里methods是（‘GET’，）
        raise TypeError('Allowed methods have to be iterables of strings, '
                        'for example: @app.route(..., methods=["POST"])')
    methods = set(item.upper() for item in methods)

    # Methods that should always be added
    required_methods = set(getattr(view_func, 'required_methods', ()))

    # starting with Flask 0.8 the view_func object can disable and
    # force-enable the automatic options handling.
    if provide_automatic_options is None:
        provide_automatic_options = getattr(view_func,
            'provide_automatic_options', None)

    if provide_automatic_options is None:
        if 'OPTIONS' not in methods:
            provide_automatic_options = True
            required_methods.add('OPTIONS')
        else:
            provide_automatic_options = False

    # Add the required methods now.
    methods |= required_methods

    rule = self.url_rule_class(rule, methods=methods, **options)
    rule.provide_automatic_options = provide_automatic_options

    self.url_map.add(rule)
    if view_func is not None:
        old_func = self.view_functions.get(endpoint)
        if old_func is not None and old_func != view_func:
            raise AssertionError('View function mapping is overwriting an '
                                 'existing endpoint function: %s' % endpoint)
        self.view_functions[endpoint] = view_func