Golang slice附加内置函数返回值

Question

The return value of slice2 of this code is [[1 1][1 1]].
And that got me confuse because I was expecting [[0 0][1 1]].
I can't figure it out why is returning [[1 1][1 1]] and not [[0 0][1 1]].
I would appreciate if someone can explain that. Thanks.

slice := []int{0, 0}
slice2 := [][]int{}

for i := range slice {
    slice[0] = i
    slice[1] = i
    slice2 = append(slice2, slice)
}
fmt.Println(slice2)

You can check the code in this link play.golang.org

Answer 1

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).

In your case your are appending a slice(pointer) not the slice's values. To get the desired result you have to declare a new slice in each iteration and append the new slice to slice2.

func main() {
    slice := []int{0, 0}
    slice2 := [][]int{}

    for i := range slice {
        ns := []int{0, 0}
        ns[0] = i
        ns[1] = i
        slice2 = append(slice2, ns)
    }
    fmt.Println(slice2) // Outputs: [[0 0] [1 1]]
}

Playground