[Go] Embedding a pointer.

package main

import (
    "log"
)

type Point struct {
    x float64
    y float64
}

func NewPoint(x float64, y float64) *Point {
    p := new(Point)

    p.SetX(x)
    p.SetY(y)

    return p
}

func (p *Point) X() float64 {
    return p.x
}

func (p *Point) Y() float64 {
    return p.y
}

func (p *Point) SetX(x float64) {
    p.x = x
}

func (p *Point) SetY(y float64) {
    p.y = y
}

type Point3D struct {
    // Point is embedded as a pointer
    *Point
    z float64
}

func NewPoint3D(x float64, y float64, z float64) *Point3D {
    p := new(Point3D)

    // Forward promotion
    p.Point = NewPoint(x, y)

    // Forward promotion
    p.Point.SetX(x)
    p.Point.SetY(y)

    p.SetZ(z)

    return p
}

func (p *Point3D) Z() float64 {
    return p.z
}

func (p *Point3D) SetZ(z float64) {
    p.z = z
}

func main() {
    p := NewPoint3D(1, 2, 3)

    // GetX method is from Point
    if !(p.X() == 1) {
        log.Fatal("Wrong value")
    }

    // GetY method is from Point
    if !(p.Y() == 2) {
        log.Fatal("Wrong value")
    }

    // GetZ method is from Point3D
    if !(p.Z() == 3) {
        log.Fatal("Wrong value")
    }
}