如何为指针参数分配地址

Question

I'm trying to write a function that takes in a struct pointer and points it to another address.

I know I can simply write a function that takes a pointer and manipulates struct fields like so:

func ManipulateStruct(myPointer *MyStruct) {
    myPointer.Field1 = "new value"
    myPointer.Field2 = 10
}

However, is it possible to write something like:

func ManipulateStruct(myPointer *MyStruct) {
    newPointer := new(MyStruct)
    newPointer.Field1 = "new value"
    newPointer.Field2 = 10

    // myPointer = &newPointer <-- illegal
    // cannot use &newPointer (type **MyStruct) as type *MyStruct in assignment

    myPointer = newPointer
}

Answer 1

Using new makes a pointer to your struct so you need pointer like this:

package main

import "fmt"

func main() {
    var ptr *MyStruct
    ManipulateStruct(&ptr)
    fmt.Println(ptr)
}
func ManipulateStruct(myPointer **MyStruct) {
    newPointer := new(MyStruct)
    newPointer.Field1 = "new value"
    newPointer.Field2 = 10
    *myPointer = newPointer
}

type MyStruct struct {
    Field1 string
    Field2 int
}

Output:

&{new value 10}