good good study, day day up!

vendor/gopl.io/ch4/embed/main.go

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+// 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}
+	//!-
+}