Golang : Fix cannot convert buffer (type *bytes.Buffer) to type string error



Tags : golang convert-buffer bytes-buffer string

Encountered these similar error messages while working on the previous tutorials on how to reset buffer and writing to http.ResponseWriter :

cannot convert buffer (type *bytes.Buffer) to type string

and

cannot use buffer (type *bytes.Buffer) as type []byte in argument to w.Write

1. Cannot convert buffer (type *bytes.Buffer) to type string solution

the error message is generated because of attempt to convert the bytes.Buffer directly to string type with string() function.

 fmt.Println(string(buffer))

to fix this error. Use buffer.String() or string(buffer.Bytes())

 package main

 import (
 "bytes"
 "fmt"
 )

 func main() {

 buffer := bytes.NewBuffer([]byte("Hello World!"))

 fmt.Println(buffer.String())

 // or
 // fmt.Println(string(buffer.Bytes())

 }

2. Cannot use buffer (type *bytes.Buffer) as type []byte in argument to w.Write solution

Writing buffer directly to http.ResponseWriter will cause error

 func SayHelloWorld(w http.ResponseWriter, r *http.Request) {
 buffer := bytes.NewBuffer([]byte("Hello World!"))
 w.Write(buffer)  // <--- wrong!
 }

the solution is to use

 w.Write(buffer.Bytes())

or use Buffer.WriteTo() function.

 func SayHelloWorld(w http.ResponseWriter, r *http.Request) {
 buffer := bytes.NewBuffer([]byte("Hello World!"))
 buffer.WriteTo(w)
 }

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Tags : golang convert-buffer bytes-buffer string

By Adam Ng

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