从app.route装饰器引发对endpoint的思考

还是先来看看源码

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):
        endpoint = options.pop('endpoint', None)
        self.add_url_rule(rule, endpoint, f, **options)
        return f
    return decorator

route传入了**options这样一个字典，一般我们会传方法methods进去，GET、POST，如果不自己设置endpoint=....的话默认就是No。
然后进入add_url_rule函数看一看：

def add_url_rule(self, rule, endpoint=None, view_func=None, **options):

    if endpoint is None:
        endpoint = _endpoint_from_view_func(view_func)
    options['endpoint'] = endpoint
    methods = options.pop('methods', None)

...
...
...

    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

这里我截取了一些重点的，可以看到如果endpoint为None，会调用_endpoint_from_view_func函数来给endpoint赋值，
看一下_endpoint_from_view_func的代码：

def _endpoint_from_view_func(view_func):

"""Internal helper that returns the default endpoint for a given
function.  This always is the function name.
"""
assert view_func is not None, 'expected view func if endpoint ' \
                              'is not provided.'
return view_func.__name__

可以看到将视图函数名赋值给了endpoint，所以如果我们创建视图函数时不在**options中指明endpoint的话，默认就是视图函数名，
后半部分进行了判断，保证了endpoint的唯一，并将view_func保存在view_functions这个字典中，并且和endpoint形成映射关系，还将路径加入到当前应用中， 这样做的好处是，当我们用url_for()从一个endpoint来找到一个URL时，可以顺着这个映射关系来找，而不用写URL， 常见的用法是url_for(blueprint.endpoint,parm=val...)进行重定向，这样可以获取一个视图函数的路径，传给redirect()，
redirect(location,code=302)函数会把接收的参数作为响应body中的Location字段返回给客户端，并且默认是302临时重定向。

def redirect(location, code=302, Response=None):
...
...

#为Location字段赋值，返回给客户端进行重定向
response.headers['Location'] = location
        return response

总结：
URL《————》endpoint《————》view
一个视图函数的endpoint如果不设置那么就是视图函数名。
为URL和view搭起桥梁，使得整个后端框架更加灵活。
url_for(.endpoint)返回的是视图函数对应的URL，URL是对应视图函数装饰器传入的值。