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我們?cè)?Router 解讀那一章，最后提到了一個(gè) method 的問題，那現(xiàn)在這一章，我們就來看一下，這個(gè) method 是怎么解讀的。

代碼事例

def get_urls(self):
        """
        Use the registered viewsets to generate a list of URL patterns.
        """
        ret = []

        for prefix, viewset, basename in self.registry:
            lookup = self.get_lookup_regex(viewset)
            routes = self.get_routes(viewset)

            for route in routes:

                # Only actions which actually exist on the viewset will be bound
                mapping = self.get_method_map(viewset, route.mapping)
                if not mapping:
                    continue

                # Build the url pattern
                regex = route.url.format(
                    prefix=prefix,
                    lookup=lookup,
                    trailing_slash=self.trailing_slash
                )
                view = viewset.as_view(mapping, **route.initkwargs)
                name = route.name.format(basename=basename)
                ret.append(url(regex, view, name=name))

        return ret

依然回到 get_urls 函數(shù)中

lookup = self.get_lookup_regex(viewset)
routes = self.get_routes(viewset)

在遍歷 registry列表的時(shí)候，通過 viewset獲取了 lookup 與 routes。

lookup

def get_lookup_regex(self, viewset, lookup_prefix=''):
        """
        Given a viewset, return the portion of URL regex that is used
        to match against a single instance.

        Note that lookup_prefix is not used directly inside REST rest_framework
        itself, but is required in order to nicely support nested router
        implementations, such as drf-nested-routers.

        https://github.com/alanjds/drf-nested-routers
        """
        base_regex = '(?P<{lookup_prefix}{lookup_url_kwarg}>{lookup_value})'
        # Use `pk` as default field, unset set.  Default regex should not
        # consume `.json` style suffixes and should break at '/' boundaries.
        lookup_field = getattr(viewset, 'lookup_field', 'pk')
        lookup_url_kwarg = getattr(viewset, 'lookup_url_kwarg', None) or lookup_field
        lookup_value = getattr(viewset, 'lookup_value_regex', '[^/.]+')
        return base_regex.format(
            lookup_prefix=lookup_prefix,
            lookup_url_kwarg=lookup_url_kwarg,
            lookup_value=lookup_value
        )

該函數(shù)從viewset中獲取 lookup_field、lookup_url_kwarg、lookup_value_regex 屬性，然后格式化成 base_regex。

routes

known_actions = flatten([route.mapping.values() for route in self.routes if isinstance(route, Route)])

self.routes 是 SimpleRouter 類初始化的一個(gè)變量

    routes = [
        # List route.
        Route(
            url=r'^{prefix}{trailing_slash}$',
            mapping={
                'get': 'list',
                'post': 'create'
            },
            name='{basename}-list',
            initkwargs={'suffix': 'List'}
        ),
        # Dynamically generated list routes.
        # Generated using @list_route decorator
        # on methods of the viewset.
        DynamicListRoute(
            url=r'^{prefix}/{methodname}{trailing_slash}$',
            name='{basename}-{methodnamehyphen}',
            initkwargs={}
        ),
        # Detail route.
        Route(
            url=r'^{prefix}/{lookup}{trailing_slash}$',
            mapping={
                'get': 'retrieve',
                'put': 'update',
                'patch': 'partial_update',
                'delete': 'destroy'
            },
            name='{basename}-detail',
            initkwargs={'suffix': 'Instance'}
        ),
        # Dynamically generated detail routes.
        # Generated using @detail_route decorator on methods of the viewset.
        DynamicDetailRoute(
            url=r'^{prefix}/{lookup}/{methodname}{trailing_slash}$',
            name='{basename}-{methodnamehyphen}',
            initkwargs={}
        ),
    ]

這個(gè) routes 包含了2個(gè) Route, 一個(gè)DynamicListRoute，一個(gè)DynamicDetailRoute.從直觀上看，應(yīng)該是2個(gè) Route 分別提供了get,create 以及 retrieve, update, partial_update, delete兩種格式
，DynamicListRoute 以及 DynamicDetailRoute 包含了 listroute 以及 detail route 兩種格式

再往下閱讀函數(shù)，可以發(fā)現(xiàn)通過 @detail_route 以及 @list_route定義的路由，不能使用已經(jīng)存在的 method 名稱，并定義了獲取動(dòng)態(tài)路由的函數(shù)。
這樣，路由中就包含了通用的 list, create, update, retrieve, delete 等，還包含了 list_route以及 detail_route 定義的路由。

get_method_map

生成 routes 后，就可以查看 viewset 類中是否有對(duì)應(yīng) method 的函數(shù)了。生成的 mapping，傳入 as_view 函數(shù)，供后續(xù)使用。

傳入 as_view 函數(shù)后，能看到函數(shù)設(shè)置了http 請(qǐng)求方法所對(duì)應(yīng)的處理函數(shù)，比如http get 方法，就調(diào)用 list 函數(shù)。

注:

http_method_names

http_method_names = ['get', 'post', 'put', 'patch', 'delete', 'head', 'options', 'trace']

我們會(huì)在函數(shù)中看到有 cls.http_method_names 的表達(dá)式，從代碼中，一層一層的讀取代碼，發(fā)現(xiàn) http_method_names 是 django 中 view, generic 里面的函數(shù)，內(nèi)容就是 http 允許的方法