166

I am trying to convert a bool called isExist to a string (true or false) by using string(isExist) but it does not work. What is the idiomatic way to do this in Go?

Casper
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    `strconv.FormatBool(t)` to set `true` to “true”. `strconv.ParseBool("true")` to set “true” to `true`. See https://stackoverflow.com/a/62740786/12817546. –  Jul 09 '20 at 10:18

4 Answers4

275

use the strconv package

docs

strconv.FormatBool(v)

func FormatBool(b bool) string FormatBool returns "true" or "false"
according to the value of b

Brrrr
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45

The two main options are:

  1. strconv.FormatBool(bool) string
  2. fmt.Sprintf(string, bool) string with the "%t" or "%v" formatters.

Note that strconv.FormatBool(...) is considerably faster than fmt.Sprintf(...) as demonstrated by the following benchmarks:

func Benchmark_StrconvFormatBool(b *testing.B) {
  for i := 0; i < b.N; i++ {
    strconv.FormatBool(true)  // => "true"
    strconv.FormatBool(false) // => "false"
  }
}

func Benchmark_FmtSprintfT(b *testing.B) {
  for i := 0; i < b.N; i++ {
    fmt.Sprintf("%t", true)  // => "true"
    fmt.Sprintf("%t", false) // => "false"
  }
}

func Benchmark_FmtSprintfV(b *testing.B) {
  for i := 0; i < b.N; i++ {
    fmt.Sprintf("%v", true)  // => "true"
    fmt.Sprintf("%v", false) // => "false"
  }
}

Run as:

$ go test -bench=. ./boolstr_test.go 
goos: darwin
goarch: amd64
Benchmark_StrconvFormatBool-8       2000000000           0.30 ns/op
Benchmark_FmtSprintfT-8             10000000           130 ns/op
Benchmark_FmtSprintfV-8             10000000           130 ns/op
PASS
ok      command-line-arguments  3.531s
maerics
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13

In efficiency is not too much of an issue, but genericity is, just use fmt.Sprintf("%v", isExist), as you would for almost all the types.

akim
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10

you may use strconv.FormatBool like this: 

package main

import "fmt"
import "strconv"

func main() {
    isExist := true
    str := strconv.FormatBool(isExist)
    fmt.Println(str)        //true
    fmt.Printf("%q\n", str) //"true"
}

or you may use fmt.Sprint like this: 

package main

import "fmt"

func main() {
    isExist := true
    str := fmt.Sprint(isExist)
    fmt.Println(str)        //true
    fmt.Printf("%q\n", str) //"true"
}

or write like strconv.FormatBool: 

// FormatBool returns "true" or "false" according to the value of b
func FormatBool(b bool) string {
    if b {
        return "true"
    }
    return "false"
}