What's the difference between ResponseWriter.Write and io.WriteString?

Question

I\'ve seen three ways of writing content to HTTP response:

func Handler(w http.ResponseWriter, req *http.Request) {
    io.WriteString(w, \"blabla.\\n\")
}
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Answer 1

As you can see from here(ResponseWriter), that it is a interface with Write([]byte) (int, error) method.

So in io.WriteString and fmt.Fprintf both are taking Writer as 1st argument which is also a interface wrapping Write(p []byte) (n int, err error) method

type Writer interface {
    Write(p []byte) (n int, err error)
}

So when you call io.WriteString(w,"blah") check here

func WriteString(w Writer, s string) (n int, err error) {
  if sw, ok := w.(stringWriter); ok {
      return sw.WriteString(s)
  }
  return w.Write([]byte(s))
}

or fmt.Fprintf(w, "blabla") check here

func Fprintf(w io.Writer, format string, a ...interface{}) (n int, err error) {
   p := newPrinter()
   p.doPrintf(format, a)
   n, err = w.Write(p.buf)
   p.free()
   return
}

you are just calling Write Method indirectly as you are passing ResponseWriter variable in both methods.

So just why not call it directly using w.Write([]byte("blabla\n")). I hope you got your answer.

PS: there's also a different way to use that, if you want to send it as JSON response.

json.NewEncoder(w).Encode(wrapper)
//Encode take interface as an argument. Wrapper can be:
//wrapper := SuccessResponseWrapper{Success:true, Data:data}