传递切片时，为什么Go中的函数附加功能可以参考使用？

Question

In the next code I'm trying to add an element of a slice of slices, but as Go works with reference, how can I use this by using the b slice by value?

package main

import (
    "fmt"
)

func main() {
    a := []int{1}
    arr := [][]int{a}

    b := []int{2}

    arr = append(arr, b)
    fmt.Println(arr)

    b[0] = 3
    arr = append(arr, b)   

    fmt.Println(arr)
}

I expected that the last Println was [[1] [2] [3]], but it's [[1] [3] [3]].

Answer 1

There is no way to insert a slice "by value"; you need to make a copy of the slice before inserting it:

package main

import (
    "fmt"
)

func copy_ints(c []int) []int {
    s := make([]int, len(c))
    copy(s, c)
    return s
}

func main() {
    a := []int{1}
    arr := [][]int{copy_ints(a)}

    b := []int{2}

    arr = append(arr, copy_ints(b))
    fmt.Println(arr)

    b[0] = 3
    arr = append(arr, copy_ints(b))

    fmt.Println(arr)
}

https://play.golang.org/p/Tds5FGj3nf