update book code

eBook/examples/chapter_11/reflect_struct.go

@@ -0,0 +1,47 @@
+// reflect.go
+package main
+
+import (
+	"fmt"
+	"reflect"
+)
+
+type NotknownType struct {
+	s1, s2, s3	string
+}
+
+func (n NotknownType) String() string {
+	return n.s1 + " - " + n.s2 + " - " + n.s3
+}
+
+// variable to investigate:
+var secret interface {} = NotknownType{"Ada", "Go", "Oberon"}
+
+func main() {
+	value := reflect.ValueOf(secret)  // <main.NotknownType Value>
+	typ := reflect.TypeOf(secret)   // main.NotknownType
+	// alternative:
+	//typ := value.Type()  // main.NotknownType
+	fmt.Println(typ)
+	knd := value.Kind()  // struct
+	fmt.Println(knd)
+
+	// iterate through the fields of the struct:
+	for i:= 0; i < value.NumField(); i++ {
+		fmt.Printf("Field %d: %v\n", i, value.Field(i))
+		// error: panic: reflect.Value.SetString using value obtained using unexported field
+		//value.Field(i).SetString("C#") 
+	}
+	
+	// call the first method, which is String():
+	results := value.Method(0).Call(nil)
+	fmt.Println(results)  // [Ada - Go - Oberon]
+}
+/* Output:
+main.NotknownType
+struct
+Field 0: Ada
+Field 1: Go
+Field 2: Oberon
+[Ada - Go - Oberon]
+*/