49

I am a newbie in Go. I can't find any official docs showing how to merge multiple strings into a new string.

What I'm expecting:

Input: "key:", "value", ", key2:", 100

Output: "Key:value, key2:100"

I want to use + to merge strings like in Java and Swift if possible.

Darshan Rivka Whittle
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Yi Jiang
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    Possible duplicate of [Golang: format a string without printing?](http://stackoverflow.com/questions/11123865/golang-format-a-string-without-printing) – icza Feb 25 '16 at 00:19
  • Does this answer your question? [Format a Go string without printing?](https://stackoverflow.com/questions/11123865/format-a-go-string-without-printing) – jub0bs Mar 31 '22 at 05:19

5 Answers5

84

I like to use fmt's Sprintf method for this type of thing. It works like Printf in Go or C only it returns a string. Here's an example:

output := fmt.Sprintf("%s%s%s%d", "key:", "value", ", key2:", 100)

Go docs for fmt.Sprintf

Arnav Borborah
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evanmcdonnal
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26

You can use strings.Join, which is almost 3x faster than fmt.Sprintf. However it can be less readable.

output := strings.Join([]string{"key:", "value", ", key2:", strconv.Itoa(100)}, "")

See https://play.golang.org/p/AqiLz3oRVq

strings.Join vs fmt.Sprintf

BenchmarkFmt-4       2000000           685 ns/op
BenchmarkJoins-4     5000000           244 ns/op

Buffer

If you need to merge a lot of strings, I'd consider using a buffer rather than those solutions mentioned above.

basgys
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    Well, if you use strconv.Itoa then you can as well concatenate strings with + – Colin Pitrat Oct 26 '17 at 15:40
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    @ColinPitrat Due to an issue on the go compiler, strings.Join of 2 or 3 elements use +, but above that it creates a byte slice for a more efficient concatenation. If you have more than two elements to concatenate, I would strongly recommend to use strings.Join. – basgys Oct 29 '17 at 21:41
2

You can simply do this:

package main

    import (
        "fmt" 
        "strconv"
    )
    
    func main() {

         
         result:="str1"+"str2"+strconv.Itoa(123)+"str3"+strconv.Itoa(12)
         fmt.Println(result)
         
    }

Using fmt.Sprintf()

var s1="abc"
var s2="def"
var num =100
ans:=fmt.Sprintf("%s%d%s", s1,num,s2);
fmt.Println(ans);
Sandeep Patel
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-1

You can use text/template:

package main

import (
   "text/template"
   "strings"
)

func format(s string, v interface{}) string {
   t, b := new(template.Template), new(strings.Builder)
   template.Must(t.Parse(s)).Execute(b, v)
   return b.String()
}

func main() {
   s := struct{
      Key string
      Key2 int
   }{"value", 100}
   f := format("key:{{.Key}}, key2:{{.Key2}}", s)
   println(f)
}

or fmt.Sprint:

package main
import "fmt"

func main() {
   s := fmt.Sprint("key:", "value", ", key2:", 100)
   println(s)
}
Zombo
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-1

Here's a simple way to combine string and integer in Go Lang(Version: go1.18.1 Latest)

package main

import (
    "fmt"
    "io"
    "os"
)

func main() {
    const name, age = "John", 26
    s := fmt.Sprintf("%s is %d years old.\n", name, age)
    io.WriteString(os.Stdout, s) // Ignoring error for simplicity.
}

Output:

John is 26 years old.

Gaurav Vetron
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