Pointer/value receiver

💻 Tech

One common mistake in Go is trying to change the value of struct inside a function whose receiver is using value semantics. A value receiver only receives a copy of struct and cannot mutate the value of the struct while a pointer receiver can perform mutation.

package main

import "fmt"

type A struct {
	Name string
}

func (a *A) Change1(name string) {
	fmt.Println("Inside pointer semantics receiver:", name)
	a.Name = name
}

func (a A) Change2(name string) {
	fmt.Println("Inside value semantics receiver:", name)
	a.Name = name
}

func main() {
	a := A{}
	fmt.Println("Initial value:", a.Name)
	a.Change2("Vinicius")
	fmt.Println("Using value semantics receiver:", a.Name)
	a.Change1("Beau")
	fmt.Println("Using pointer semantics receiver:", a.Name)
}

Initial value:
Inside value semantics receiver: Vinicius
Using value semantics receiver:
Inside pointer semantics receiver: Beau
Using pointer semantics receiver: Beau