struct.go

// All material is licensed under the Apache License Version 2.0, January 2016
// http://www.apache.org/licenses/LICENSE-2.0

// Example shows how reflection provides readability and simplicity.
package main

import (
	"fmt"
	"reflect"
)

// user represents a basic user in the system.
type user struct {
	name     string
	age      int
	building float32
	secure   bool
	roles    []string
}

func main() {

	// Create a value of the conrete type user.
	u := user{
		name:     "Cindy",
		age:      27,
		building: 321.45,
		secure:   true,
		roles:    []string{"admin", "developer"},
	}

	// Display the value we are passing.
	display(&u)
}

// display will display the details of the provided value.
func display(v interface{}) {

	// Inspect the concrete type value that is passed in.
	rv := reflect.ValueOf(v)

	// Was the value a pointer value.
	if rv.Kind() == reflect.Ptr {

		// Get the value that the pointer points to.
		rv = rv.Elem()
	}

	// Based on the Kind of value customize the display.
	switch rv.Kind() {

	case reflect.Struct:
		displayStruct(rv)
	}
}

// displayStruct will display details about a struct type.
func displayStruct(rv reflect.Value) {

	// Show each field and the field information.
	for i := 0; i < rv.NumField(); i++ {

		// Get field information for this field.
		fld := rv.Type().Field(i)
		fmt.Printf("Name: %s\tKind: %s", fld.Name, fld.Type.Kind())

		// Display the value of this field.
		fmt.Printf("\tValue: ")
		displayValue(rv.Field(i))

		// Add an extra line feed for the display.
		fmt.Println()
	}
}

// displayValue extracts the native value from the reflect value that is
// passed in and properly displays it.
func displayValue(rv reflect.Value) {

	// Display each value based on its Kind.
	switch rv.Type().Kind() {

	case reflect.String:
		fmt.Printf("%s", rv.String())

	case reflect.Int:
		fmt.Printf("%v", rv.Int())

	case reflect.Float32:
		fmt.Printf("%v", rv.Float())

	case reflect.Bool:
		fmt.Printf("%v", rv.Bool())

	case reflect.Slice:
		for i := 0; i < rv.Len(); i++ {
			displayValue(rv.Index(i))
			fmt.Printf(" ")
		}
	}
}