Specify a Go struct method where an attempted struct value update should be an error


This Content is from Stack Overflow. Question asked by Bambam

Can the ReadOnlyFunc be specified differently so the “p.a = 5” line would be picked up as a compile-time error (or at least a warning)?

package main

import "fmt"

type Pair struct {
    a int
    b int

func (p Pair) ReadOnlyFunc() {
    p.a = 5
    fmt.Println("ReadOnlyFunc p=", p)

func main() {
    p := &Pair{a: 1, b: 1}
    fmt.Println("main p=", p)

Outputs as expected with the change local-only:

ReadOnlyFunc p= {5 1}
main p= &{1 1}

and adding a ‘*’ so func (p *Pair) ReadOnlyFunc() updates the shared copy as expected so:

ReadOnlyFunc p= {5 1}
main p= &{5 1}


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