那flask是如何将路由与视图函数绑定的呢？在Flask类的内部是这样定义的：
def route(self, rule, **options): def decorator(f): self.add_url_rule(rule, f.__name__, **options) self.view_functions[f.__name__] = f return f return decoratorself.view_functions = {}def add_url_rule(self, rule, endpoint, **options): options['endpoint'] = endpoint options.setdefault('methods', ('GET',)) self.url_map.add(Rule(rule, **options))self.url_map = Map() 可以看到，route定义了一个装饰品，通过add_url_rule方法将URL与视图函数的名字（即enpoint）绑定，并通过view_function字典将开发者定义的函数添加到视图函数里，形式为{ 函数名: 函数 }。也就是说，URL并不直接与处理函数绑定。URL是与endpoint绑定，而endpoint才与处理函数绑定。endpoint与处理函数通过view_fuction{}字典映射，这很好理解，不过URL与endpoint的绑定就需要多花点心思来理解了，因为引入了werkzeug中的Map和Rule。Map和Rule从字面上很容易理解 为“所有映射关系”和“产生一对新的映射关系”。
Flask类中dispatch_request()方法使用了view_fuction{}字典：
def dispatch_request(self): try: endpoint, values = self.match_request() return self.view_functions[endpoint](**values) except HTTPException, e: handler = self.error_handlers.get(e.code) if handler is None: return e return handler(e) except Exception, e: handler = self.error_handlers.get(500) if self.debug or handler is None: raise return handler(e)
获取endpoint的关键在于match_request()方法：
def match_request(self): """Matches the current request against the URL map and also stores the endpoint and view arguments on the request object is successful, otherwise the exception is stored. """ rv = _request_ctx_stack.top.url_adapter.match() request.endpoint, request.view_args = rv return rv
这里的match方法是werkzeug中MapAdapter类定义的方法。
>>> m = Map([... Rule('/', endpoint='index'),... Rule('/downloads/', endpoint='downloads/index'),... Rule('/downloads/ ', endpoint='downloads/show')... ])>>> urls = m.bind("example.com", "/")>>> urls.match("/", "GET")('index', {})>>> urls.match("/downloads/42")('downloads/show', { 'id': 42})And here is what happens on redirect and missing URLs:>>> urls.match("/downloads")Traceback (most recent call last): ...RequestRedirect: http://example.com/downloads/>>> urls.match("/missing")Traceback (most recent call last): ...NotFound: 404 Not Found 这里展示了Map和Rule的主要几个功能：映射关系的添加、绑定和匹配。
总结一下路由匹配的过程：
- 通过@app.route或app.add_url_map()将URL和endpoint绑定，将endpoint和处理函数绑定。
- 将请求URL通过match方法取得endpoint及相关参数。
- 通过view_fuction{}字典获取endpoint对应的函数，将相关参数传入，进行处理。
