How do you make multiple interfaces reference the same value?

gabetucker22 0
Viewed 124

I would like to make two interfaces reference the same value (meaning if you update one, the other will update to the same thing):

package main

import (
    "fmt"
    "reflect"
)

func main(){
    var a, b any

    a = "Hi"

    b = reflect.ValueOf(&a).Elem()
    a = reflect.ValueOf(&b).Elem()

    b = "Howdy"

    fmt.Println(a)
    fmt.Println(b)
}

PRINT LOGS

Howdy
Howdy

PLAYGROUND: https://go.dev/play/p/qizVO42UaUj

This code works as intended, aside from the fact that a and b are not interfaces. So when I convert them to interfaces like so...

package main

import (
    "fmt"
    "reflect"
)

func main(){
    var a, b any

    a = "Hi"

    b = reflect.ValueOf(&a).Elem().Interface()
    a = reflect.ValueOf(&b).Elem().Interface()

    b = "Howdy"

    fmt.Println(a)
    fmt.Println(b)
}

PRINT LOGS

Hi
Howdy

PLAYGROUND: https://go.dev/play/p/jCpuepBJYdD

...the code no longer works as intended.

Is there a way to use the interface data type rather than the reflect.Value data type while maintaining that the two interfaces reference the same value?

memory-management reflection interface memory go
1 Answers

Simple Solution

Figured it out—no need to use reflection. Storing the value's address in the interface will allow you to accomplish this by using a type assertion to an interface pointer and dereferencing:

package main

import "fmt"

func main() {
    var object any
    object = "Hi"

    var a, b any
    a = &object
    b = &object

    *a.(*any) = "Howdy"

    fmt.Println(*a.(*any))
    fmt.Println(*b.(*any))
}

PRINT LOGS

Howdy
Howdy

PLAYGROUND: https://go.dev/play/p/LEx8MR4ZK06

Using Multiple Functions

If you would like to abstract away the type-assertion and derefencing:

package main

import "fmt"

func getStuff(a any) any {
    return *a.(*any)
}

func setStuff(a, to any) {
    *a.(*any) = to
}

func main() {
    var object any
    object = "Hi"

    var a, b any
    a = &object
    b = &object

    setStuff(a, "Howdy")

    fmt.Println(getStuff(a))
    fmt.Println(getStuff(b))
}

PRINT LOGS

Howdy
Howdy

PLAYGROUND: https://go.dev/play/p/RUX4cu2Cx2o

gabetucker220
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