How to convert interface to string in Go

Type casting an interface to a string in go
Created
Modified

Using fmt.Sprintf Function

To convert interface to string in Go, use fmt.Sprintf function.

Sprintf formats according to a format specifier and returns the resulting string.

package main

import "fmt"

var x = []interface{}{
  "abc",
  1,
  3.14,
  []int{1, 2, 3},
  struct {
    A int
    B string
  }{
    A: 10,
    B: "code",
  },
}

func main() {

  // Method fmt.Sprintf("value: %v", v)
  for _, v := range x {
    str := fmt.Sprintf("%v", v)
    fmt.Println(str)
  }

  // Method fmt.Sprint(v)
  for _, v := range x {
    str := fmt.Sprint(v)
    fmt.Println(str)
  }

}
abc
1
3.14
[1 2 3]
{10 code}

abc
1
3.14
[1 2 3]
{10 code}

fmt.Sprint(val) is equivalent to fmt.Sprintf("%v", val)

If the %v verb is used with the # flag (%#v) and the operand implements the GoStringer interface, that will be invoked.

// Method fmt.Sprintf("value: %#v", v)
  for _, v := range x {
    str := fmt.Sprintf("%#v", v)
    fmt.Println(str)
  }
"abc"
1
3.14
[]int{1, 2, 3}
struct { A int; B string }{A:10, B:"code"}

Type Assertion

A type assertion provides access to an interface value's underlying concrete value.

package main

import "fmt"

func main() {

  var i interface{} = "golang"

  // Method t := i.(T)
  s := i.(string)
  fmt.Println(s)

  // Method t, ok := i.(T)
  s, ok := i.(string)
  fmt.Println(s, ok)

  f := i.(float64) // panic
  fmt.Println(f)
}

golang
golang true
panic: interface conversion: interface {} is string, not float64

If i does not hold a T, the statement will trigger a panic.

Related Tags

#convert# #interface# #string#

MORE FROM THE INSTALLMD