Tour of Go 2.0

Choosing a value or pointer receiver

So when do you use a pointer receiver vs a value receiver? Two good reasons to reach for a pointer:

  1. You need to modify the receiver.
  2. You want to avoid copying a large struct on every call.

In this example, Abs doesn’t actually need to modify anything — but it still uses *Vertex to stay consistent with Scale.

That’s the rule: pick one style for all methods on a type. Don’t mix value and pointer receivers on the same type. It causes confusion — and problems with interfaces, which you’ll see soon.

main.go ▶ Run in Playground 
package main

import (
	"fmt"
	"math"
)

type Vertex struct {
	X, Y float64
}

func (v *Vertex) Scale(f float64) {
	v.X = v.X * f
	v.Y = v.Y * f
}

func (v *Vertex) Abs() float64 {
	return math.Sqrt(v.X*v.X + v.Y*v.Y)
}

func main() {
	v := &Vertex{3, 4}
	fmt.Printf("Before scaling: %+v, Abs: %v\n", v, v.Abs())
	v.Scale(5)
	fmt.Printf("After scaling: %+v, Abs: %v\n", v, v.Abs())
}