flask/app.py-add_url_rule源码分析

之前分析route方法的时候，可以看到中间会调用add_url_rule方法，add_url_rule方法和route方法一样属于Flask这个类的。

add_url_rule方法主要用来连接url规则。具体工作方法和route类似。如果提供了视图函数，它将会和endpoint名字一起被注册

#装饰器使用方法：
@app.route('/')
def index():
    pass

# 等同与下面这种方法：
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::
# 如果视图函数没有被提供，需要用下面语法把视图函数和endpoint对应起来
 app.view_functions['index'] = index

  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)

        # 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.
        if methods is None:
            methods = getattr(view_func, 'methods', None) or ('GET',)
        if isinstance(methods, string_types):
            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.
        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

源代码