Receivers in Go

Receivers in Go turn a function into a method, allowing it to be called on a struct or similar (similar to a class). Receivers can be a pointer, or a value. In general, all methods on a given type should have either value or pointer receivers, but not a mixture of both. Receivers are expected to modify and return (different from FP) - thus, use a pointer receiver when in doubt. Pointer receivers also have the added benefit of better memory usage, as large values dont need to be copied.

Without a receiver:

type Vertex struct {
    X, Y float64
}

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

func main() {
    v := Vertex{3, 4}
    fmt.Println(Abs(v))
}

With a receiver:

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())
}

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