update book code

eBook/examples/chapter_10/new_make.go

@@ -0,0 +1,27 @@
+// annoy1.go
+package main
+
+type Foo map[string]string
+type Bar struct {
+	thingOne string
+	thingTwo int
+}
+
+func main() {
+	// OK:
+	y := new(Bar)
+	(*y).thingOne = "hello"
+	(*y).thingTwo = 1
+	// not OK:
+	z := make(Bar) // compile error: cannot make type Bar
+	z.thingOne = "hello"
+	z.thingTwo = 1
+	// OK:
+	x := make(Foo)
+	x["x"] = "goodbye"
+	x["y"] = "world"
+	// not OK:
+	u := new(Foo)
+	(*u)["x"] = "goodbye" // !! panic !!: runtime error: assignment to entry in nil map
+	(*u)["y"] = "world"
+}