Go: convert strings in array to integer

Question

How do I convert strings in an array to integers in an array in go?

["1", "2", "3"]

to

[1, 2, 3]

I've searched for some solutions online but couldn't find it. I've tried to loop through the array and did strconv.ParseFloat(v, 64) where v is the value but it didn't work.

Answer 1

You will have to loop through the slice indeed. If the slice only contains integers, no need of ParseFloat, Atoi is sufficient.

import "fmt"
import "strconv"

func main() {
    var t = []string{"1", "2", "3"}
    var t2 = []int{}

    for _, i := range t {
        j, err := strconv.Atoi(i)
        if err != nil {
            panic(err)
        }
        t2 = append(t2, j)
    }
    fmt.Println(t2)
}

On Playground.

Answer 2

For example,

package main

import (
    "fmt"
    "strconv"
)

func sliceAtoi(sa []string) ([]int, error) {
    si := make([]int, 0, len(sa))
    for _, a := range sa {
        i, err := strconv.Atoi(a)
        if err != nil {
            return si, err
        }
        si = append(si, i)
    }
    return si, nil
}

func main() {
    sa := []string{"1", "2", "3"}
    si, err := sliceAtoi(sa)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Printf("%q %v\n", sa, si)
}

Output:

["1" "2" "3"] [1 2 3]

Playground:

http://play.golang.org/p/QwNO8R_f90

Answer 3

This is an ancient question but all the answers ignore the fact that the input length is known in advance, so it can be improved by pre-allocating the destination slice:

package main

import "fmt"
import "strconv"

func main() {
    var t = []string{"1", "2", "3"}
    var t2 = make([]int, len(t))
    
    for idx, i := range t {
        j, err := strconv.Atoi(i)
        if err != nil {
            panic(err)
        }
        t2[idx] = j
    }
    fmt.Println(t2)
}

Playground: https://play.golang.org/p/LBKnVdi_1Xz

Answer 4

A slice is a descriptor of an array segment
It consists of
- a pointer to the array,
- the length of the segment, and
- its capacity (the maximum length of the segment)

Below, string Array/Slice is converted to int Array/Slice:

package main

import (
    "fmt"
    "log"
    "strconv"
    "strings"
)

func Slice_Atoi(strArr []string) ([]int, error) {
    // NOTE:  Read Arr as Slice as you like
    var str string                           // O
    var i int                                // O
    var err error                            // O

    iArr := make([]int, 0, len(strArr))
    for _, str = range strArr {
        i, err = strconv.Atoi(str)
        if err != nil {
            return nil, err                  // O
        }
        iArr = append(iArr, i)
    }
    return iArr, nil
}

func main() {
    strArr := []string{
        "0 0 24 3 15",
        "0 0 2 5 1 5 11 13",
    }

    for i := 0; i < len(strArr); i++ {
        iArr, err := Slice_Atoi(strings.Split(strArr[i], " "))
        if err != nil {
            log.Print("Slice_Atoi failed: ", err)
            return
        }
        fmt.Println(iArr)
    }
}

Output:

[0 0 24 3 15]
[0 0 2 5 1 5 11 13]

I used in a project, so did a small optimizations from other replies, marked as // O for above, also fixed a bit in readability for others

Best of luck