interfaces: refactor

interfaces/04-interfaces/main.go

@@ -0,0 +1,35 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+func main() {
+	var (
+		minecraft = game{title: "minecraft", price: 20}
+		tetris    = game{title: "tetris", price: 5}
+		mobydick  = book{title: "moby dick", price: 10}
+	)
+
+	var my list
+	// my.list() // nil receiver is a valid value
+
+	// + only the `*game` have methods.
+	// + `game` doesn't have any methods.
+	// + `item` interface couldn't be satisfied with a `game` value.
+	// + it can only be satisfied with a `*game` value.
+	// my = my.add(minecraft)
+	my = append(my, &minecraft)
+	my = append(my, &tetris)
+	my = append(my, &mobydick)
+
+	// interface value stores a pointer to minecraft
+	minecraft.discount(.5)
+	my.list()
+
+	my.discount(.5)
+	my.list()
+}