Golang methods

Basics

In Go methods can be defined on struct and non-struct types. In this case a receiver argument ias passed between `func` keyword and the method name (`Abs`):

package main
 
import (
    "fmt"
    "math"
)
 
type Vertex struct {
    X, Y float64
}
 
func (v Vertex) Abs() float64 {
    return math.Sqrt(v.X*v.X + v.Y*v.Y)
}
 
func main() {
    v := Vertex{3, 4}
    fmt.Println(v.Abs())
}

Pointers

To modify struct values methods must be declared with pointer receivers:

package main
 
import (
    "fmt"
    "math"
)
 
type Vertex struct {
    X, Y float64
}
 
func (v Vertex) Abs() float64 {
    return math.Sqrt(v.X*v.X + v.Y*v.Y)
}
 
func (v *Vertex) Scale(f float64) {
    v.X = v.X * f
    v.Y = v.Y * f
}
 
func main() {
    v := Vertex{3, 4}
    v.Scale(10)
    fmt.Println(v.Abs())
}