从一条简单的 URL 开始

从代码开始

先来看一段代码

from flask import Flask, g, request
from functools import wraps
app = Flask(__name__)


def set_g(f):
    @wraps(f)
    def decorator(*args, **kwargs):
        g.auth = 'zadmin'
        g.scope = 5
        g.num = 0
        return f(*args, **kwargs)
    return decorator


def check_auth(f):
    @wraps(f)
    def decorator(*args, **kwargs):
        auth = g.auth
        if auth != "admin":
            print "Failed in auth"
        g.num = 20
        return f(*args, **kwargs)
    return decorator


def check_scope(f):
    #@wraps(f)
    def decorator(*args, **kwargs):
        ''' This check scope docker string '''
        scope = g.scope
        if scope not in [1, 2, 3]:
            print "Failed in scope"
        g.num = 10
        return f(*args, **kwargs)
    return decorator


@app.route('/test')
@set_g
@check_auth
@check_scope
def test():
    ''' This is function test'''
    print request.path
    print g.auth, g.scope
    print "g.num:{}".format(g.num)
    print test.__doc__
    return "test"

app.run(debug=True)

如果我访问这个 API 会在 terminal 打印什么呢？

Failed in auth
Failed in scope
/test
zadmin 5
g.num:10
This check scope docker string

装饰器会在下面的 blog 中专门说一下
这一篇只说 flask 的 route
从结果来推断，访问 API 之后函数的执行顺序是这样的：

app.route()=>set_g()=>check_auth()=>chek_scope()=>test()

flask 中的 route 到底做了什么

route

@setupmethod def route(self, rule, options): def decorator(f): endpoint = options.pop(‘endpoint’, None) self.add_url_rule(rule, endpoint, f, options) return f return decorator ​

route 是一个装饰器，负责将 URL 与 OPTION 传到 add_url_rule 这个函数中
这样的代码会更美观

add_url_rule

 def add_url_rule(self, rule, endpoint=None, view_func=None, provide_automatic_options=None, **options):
        if endpoint is None:
            endpoint = _endpoint_from_view_func(view_func)
        options['endpoint'] = endpoint
        methods = options.pop('methods', None)

        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)


        required_methods = set(getattr(view_func, 'required_methods', ()))


        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


        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

add_url_rule 处理传来的参数然后将符合规则的 url 与 method 生成一个 rule 对象
再将 rule 加到 Map() 对象中存储起来
这也是 flask 中 url 与 method 全局唯一的保证

这样看来
完整的过程是这样的：
route()=>add_url_rule()=>RULE()=>url_map.add()=>set_g()=>check_auth()=>chek_scope()=>test()

​