为什么golang追加相同的切片结果将共享一个内存地址？

Question

I thought append in go, will return a new result, but I find that append in same slice will return same memory address:

func TestRuneAppend3(t *testing.T) {
    r := make([][]rune, 256)
    r[0] = append(r[0], 99)  // c
    r[1] = append(r[0], 100) // d
    r[2] = append(r[0], 101) // e
    // I thought it would be "c cd ce", but it is "c ce ce"
    log.Println(string(r[0]), string(r[1]), string(r[2]))
}

So what is the best way if I want to the result is c cd ce?

Answer 1

Append will only allocate a new array if there isn't sufficient capacity in the slice you're appending to. If you need to have a separate array, use make to create a new slice and use copy to copy whatever you need from the original slice.

This article gives a good explanation of how slices work.