gopl-zh.github.com/vendor/gopl.io/ch4/embed/main.go

// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/

// See page 106.

// Embed demonstrates basic struct embedding.
package main

import "fmt"

type Point struct{ X, Y int }

type Circle struct {
	Point
	Radius int
}

type Wheel struct {
	Circle
	Spokes int
}

func main() {
	var w Wheel
	//!+
	w = Wheel{Circle{Point{8, 8}, 5}, 20}

	w = Wheel{
		Circle: Circle{
			Point:  Point{X: 8, Y: 8},
			Radius: 5,
		},
		Spokes: 20, // NOTE: trailing comma necessary here (and at Radius)
	}

	fmt.Printf("%#v\n", w)
	// Output:
	// Wheel{Circle:Circle{Point:Point{X:8, Y:8}, Radius:5}, Spokes:20}

	w.X = 42

	fmt.Printf("%#v\n", w)
	// Output:
	// Wheel{Circle:Circle{Point:Point{X:42, Y:8}, Radius:5}, Spokes:20}
	//!-
}