HTTP处理程序-什么时候应该使用return？

Question

I'm a little confused about http handlers and handling something like errors or redirects.

For example, if I have to redirect because of some conditional check, should I be doing the following:

func SomeHandler(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
    if thisThing != thatThing {
        log.Print("thisThing not equal to thatThing - redirecting")
        http.Redirect(w, r, "/", http.StatusTemporaryRedirect)
        return // <-- is this necessary?
    }
 }

Answer 1

The rule is: return when you're done processing, to prevent further processing.

In your case, a return is not necessary, because there is no further processing in your function. If you had further logic, though, you would want to return:

func SomeHandler(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
    if thisThing != thatThing {
        log.Print("thisThing not equal to thatThing - redirecting")
        http.Redirect(w, r, "/", http.StatusTemporaryRedirect)
        return // <-- is this necessary?
    }
    w.Header().Add("Content-Type", "application/json")
    // ... add a normal response
 }

Without a return in this case, you'll send the headers to initiate a redirect, then you'll also send a normal JSON response. That is obviously not what you want, so the return is needed.

The astute reader will note that there would be other ways to accomplish this type of control flow. An else would be an option:

func SomeHandler(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
    if thisThing != thatThing {
        log.Print("thisThing not equal to thatThing - redirecting")
        http.Redirect(w, r, "/", http.StatusTemporaryRedirect)
    } else {
        w.Header().Add("Content-Type", "application/json")
        // ... add a normal response
    }
 }

However, as your conditions grow in complexity, a return is often going to be the most readable method. But it is ultimately a style choice at that point.