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Go Interfaces Value & pointer receivers


Interface : Value and pointer receivers

  • Example with value receiver
    type myStruct struct {
    func (p1 myStruct) print1(a int) {
    func (p2 myStruct) print2(a string) {
    type myInterface interface {
    func main() {
        var ms myInterface = myStruct{} // value type for implementing an interface
When implementing an interface if you use a value type, all the methods should have value receivers. If we are implementing an interface with a pointer then we should just have the methods there.

Even if none of the functions were pointer receivers, using a pointer would have worked.

func (p2 *myStruct) print2(a string) {
// this would give an error since we have a pointer receiver

// to fix this we can do
var ms myInterface = &myStruct{}

Another Example

In the below example Vertex (the value type) doesn't implement Abser because the Abs method is defined only on *Vertex (the pointer type).
type Abser interface {
    Abs() float64

func main() {
    var a Abser
    f := MyFloat(-math.Sqrt2)
    v := Vertex{3, 4}

    a = f  // a MyFloat implements Abser
    a = &v // a *Vertex implements Abser

    // In the following line, v is a Vertex (not *Vertex)
    // and does NOT implement Abser.
    a = v


type MyFloat float64

func (f MyFloat) Abs() float64 {
    if f < 0 {
        return float64(-f)
    return float64(f)

type Vertex struct {
    X, Y float64

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

Last updated: 2022-06-29