Helper func to assign respective data to its key - go

Question

So I have this data struct:
type Parent struct {
A ChildA
B ChildB
C ChildC
D ChildD
}
type ChildA struct {
...
}
I am trying to create a helper funct such that I can reduce my LOC when it comes to variable assignment.
What I am trying to do:
func SomeHelper( SomeChild Child? ) Parent {
return Parent{
?: SomeChild
}
}
"?" can be any of the key A B C D

Answer 1

We can use variadic function and reflection.
this is the example code:
package main
import (
"errors"
"fmt"
"reflect"
)
type Parent struct {
A ChildA
B ChildB
C ChildC
D ChildD
}
type ChildA struct {
x string
}
type ChildB struct {
x string
}
type ChildC struct {
}
type ChildD struct {
}
func helper(childs ...any) (Parent, error) {
check := make(map[string]int)
var p Parent
for _, v := range childs {
if v == nil {
continue
}
childType := reflect.TypeOf(v)
check[childType.String()]++
if check[childType.String()] > 1 {
return p, errors.New("child must be unique")
}
switch childType.String() {
case "main.ChildA":
p.A = v.(ChildA)
case "main.ChildB":
p.B = v.(ChildB)
case "main.ChildC":
p.C = v.(ChildC)
case "main.ChildD":
p.D = v.(ChildD)
}
}
return p, nil
}
func main() {
p, err := helper(ChildA{"hello"}, ChildB{"world"}, ChildC{})
if err != nil {
panic(err)
}
fmt.Println(p)
}

Answer 2

You can use Visitor pattern.
type Parent struct {
A ChildA
B ChildB
C ChildC
}
type Child interface {
VisitParent(*Parent)
}
type ChildA struct{}
func (c ChildA) VisitParent(parent *Parent) {
parent.A = c
}
type ChildB struct{}
func (c ChildB) VisitParent(parent *Parent) {
parent.B = c
}
type ChildC struct{}
func (c ChildC) VisitParent(parent *Parent) {
parent.C = c
}
func SomeHelper(someChild Child) Parent {
parent := Parent{}
someChild.VisitParent(&parent)
return parent
}