从Go中的数组返回指针数组

Question

Just so you know, I am quite new to Go.

I have been trying to make a function like this:

func PointersOf(slice []AnyType) []*AnyType{
    //create an slice of pointers to the elements of the slice parameter
}

It is like doing &slice[idx] for all elements in the slice, but I am having trouble with how to type my parameters and return type, as well as how to create the slice itself.

This method needs to work for slices of built-in types, as well as for slices of structs and slices of pointers to built-in types/structs

After invoking this function it would be preferable if I don't have to cast the pointer slice

---

Edit: The reason why I need this method is to have a generic way to use the elements of an array in a for ... range loop, in stead of using copies of that element. Consider:

type SomeStruct struct {
    x int
}

func main() {
    strSlice := make([]SomeStruct, 5)
    for _, elem := range strSlice {
        elem.x = 5
    }
}

This Doesn't work, because elem is a copy of the strSlice element.

type SomeStruct struct {
    x int
}

func main() {
    strSlice := make([]SomeStruct, 5)
    for _, elem := range PointersOf(strSlice) {
        (*elem).x = 5
    }
}

This however should work, since you only copy the pointer that points to an element in the original array.

Answer 1

Use the following code to loop through a slice of structs setting a field. There's no need to create a slice of pointers.

type SomeStruct struct {
  x int
}

func main() {
  strSlice := make([]SomeStruct, 5)
  for i := range strSlice {
    strSlice[i].x = 5
  }
}

<kbd>playground example</kbd>

Here's the proposed PointersOf function:

func PointersOf(v interface{}) interface{} {
  in := reflect.ValueOf(v)
  out := reflect.MakeSlice(reflect.SliceOf(reflect.PtrTo(in.Type().Elem())), in.Len(), in.Len())
  for i := 0; i < in.Len(); i++ {
    out.Index(i).Set(in.Index(i).Addr())
  }
  return out.Interface()
}

and here's how to use it:

for _, elem := range PointersOf(strSlice).([]*SomeStruct) {
    elem.x = 5
}

<kbd>playground example</kbd>