Golang嵌入具有其他隐藏方法的接口吗？

Question

I want to embed a http.ResponseWriter in a struct. That's fine, it makes sure my struct also implements http.ResponseWriter:

type MyWriter struct {
    BytesWritten int
    http.ResponseWriter
}

However, it no longer implements http.Hijacker, http.CloseNotifier or http.Flusher even though the embedded http.ResponseWriter usually does.

Is there some way to do this?

Answer 1

If you know that the response writer satisfies all of the interfaces listed in the question, then you can do this:

type allResponseWriterInterfaces {
    http.ResponseWriter
    http.Hijacker
    http.CloseNotifier
    http.Flusher
}

type MyWriter struct {
    BytesWritten int
    allResponseWriterInterfaces
}

...

aw, ok := w.(allResponseWriterInterfaces)
if !ok {
    // oops, response writer does not implement the interfaces
    // handle the error
}
mw := MyWriter{0, aw}

It get's messy if the response writer does not satisfy all of the interfaces. See the Gorilla logger for an example of handling the case where the response writer satisfies (http.ResponseWriter, http.CloseNotifier) or (http.ResponseWriter, http.CloseNotifier, http.Hijacker).