Golang HTTP路由处理程序通用包装器实现

Question

I'm trying to convert a route handler which returns response body and error instead of directly writing it to response writer. Then I want to send success/error response from the wrapper function instead.

It'll help me add tracing and metrics in a common place for all routes.

To achieve that, I tried this:

router.HandleFunc(app, "/login", WrapHandler(Login)).Methods("POST")

func WrapHandler(handler func(http.ResponseWriter, *http.Request) (interface{}, *types.HandlerErrorResponse)) func(http.ResponseWriter, *http.Request) {
    return func(w http.ResponseWriter, r *http.Request) {
        response, errResponse := handler(w, r)

        sendResponse(r.Context(), w, response, errResponse)
    }
}

Login is an interface with signature:

Login(w http.ResponseWriter, r *http.Request) (*AuthenticationResponse, *types.HandlerErrorResponse)

Now, with this code the error comes in compilation:

cannot use Login (type func(http.ResponseWriter, *http.Request) (*AuthenticationResponse, *types.HandlerErrorResponse)) as type func(http.ResponseWriter, *http.Request) (interface {}, *types.HandlerErrorResponse) in argument to WrapHandlerNew

But, to make generic Wrapper, I have to make my response body as interface.

Please let me know, how can I achieve it.

Answer 1

To make it compile Login(w http.ResponseWriter, r *http.Request) (*AuthenticationResponse, *types.HandlerErrorResponse) needs to be Login(w http.ResponseWriter, r *http.Request) (interface{}, *types.HandlerErrorResponse)

However I'd suggest you to define an inteface ( or use an existing one : io.Reader might be what you want )

Define the methods you need to access from the response and then return that.

type GenericBody interface{
    Bytes() []byte
}

Now as long as your return object implements this method, you can return it. However, the function signature will have to include this new type.