type MusicEntry struct {
Id string
Name string
Artist string
Source string
Type string
}
type MusicManager struct {
musics []MusicEntry //以数组切片作为结构体成员
}
//这里*是重点
func (m *MusicManager) Len() int {
return len(m.musics)
}
同时，在 Go 语言中，是通过接口来实现的多态。 什么是多态呢？ 比如在好学生这个接口下，不同人对好学生的定义不同，有些人认为只要成绩好就是好学生，有些人认为综合发展才是好学生，不同的人有不一样的看法，这就是多态。
接口还可以进行赋值
将对象实例赋值给接口
var xxx 接口名 = &实例对象
为什么要取地址呢？这是因为Go会将 无 * 转成 有 * 的，反之则不成立 举个栗子
type Integer int
func (a Integer) Less(b Integer) bool {
return a < b
}
func (a *Integer) Add(b Integer) {
*a += b
}
//相应地，我们定义接口LessAdder，如下：
type LessAdder interface {
Less(b Integer) bool
Add(b Integer)
}
Go语言可以根据下面的函数：
func (a Integer) Less(b Integer) bool
自动生成一个新的Less()方法：
func (a *Integer) Less(b Integer) bool {
return (*a).Less(b)
}
package main
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
"tool"
)
var MusicMN *tool.MusicManager
var id int = 1
var ctrl, signal chan int
func handleLibCommands(tokens []string) {
switch tokens[1] {
case "list":
for i := 0; i < MusicMN.Len(); i++ {
e, _ := MusicMN.Get(i)
fmt.Println(i+1, ":", e.Name, e.Artist, e.Source, e.Type)
}
case "add": {
if len(tokens) == 6 {
id++
MusicMN.Add(&tool.MusicEntry{strconv.Itoa(id),
tokens[2], tokens[3], tokens[4], tokens[5]})
} else {
fmt.Println("USAGE: lib add ")
}
}
case "remove":
if len(tokens) == 3 {
MusicMN.Remove(tokens[2])
} else {
fmt.Println("USAGE: lib remove ")
}
default:
fmt.Println("Unrecognized lib command:", tokens[1])
}
}
func handlePlayCommand(tokens []string) {
if len(tokens) != 2 {
fmt.Println("USAGE: play ")
return
}
e := MusicMN.Find(tokens[1])
if e == nil {
fmt.Println("The music", tokens[1], "does not exist.")
return
}
tool.Play(e.Source, e.Type)
}
func main() {
fmt.Println(`
Enter following commands to control the player:
lib list -- View the existing music lib
lib add -- Add a music to the music lib
lib remove -- Remove the specified music from the lib
play -- Play the specified music
`)
MusicMN = tool.NewMusicManager()
r := bufio.NewReader(os.Stdin)
for {
fmt.Print("Enter command-> ")
rawLine, _, _ := r.ReadLine()
line := string(rawLine)
if line == "q" || line == "e" {
break
}
tokens := strings.Split(line, " ")
if tokens[0] == "lib" {
handleLibCommands(tokens)
} else if tokens[0] == "play" {
handlePlayCommand(tokens)
} else {
fmt.Println("Unrecognized command:", tokens[0])
}
}
}
manager.go
package tool
import "errors"
type MusicEntry struct {
Id string
Name string
Artist string
Source string
Type string
}
type MusicManager struct {
musics []MusicEntry
}
func NewMusicManager() *MusicManager {
return &MusicManager{make([]MusicEntry, 0)}
}
func (m *MusicManager) Len() int {
return len(m.musics)
}
func (m *MusicManager) Get(index int) (music *MusicEntry, err error) {
if index < 0 || index >= len(m.musics) {
return nil, errors.New("Index out of range.")
}
return &m.musics[index], nil
}
func (m *MusicManager) Find(name string) *MusicEntry {
if len(m.musics) == 0 {
return nil
}
for _, m := range m.musics {
if m.Name == name {
return &m
}
}
return nil
}
func (m *MusicManager) Add(music *MusicEntry) {
m.musics = append(m.musics, *music)
}
func (m *MusicManager) Remove(name string) *MusicEntry {
var index int
for i, m := range m.musics {
if m.Name == name {
index=i
}
}
removedMusic := &m.musics[index]
m.musics = append(m.musics[:index],m.musics[index+1:]...)
return removedMusic
}
manager_test.go
package tool
import (
"testing"
)
func TestOps(t *testing.T) {
mm := NewMusicManager()
if mm == nil {
t.Error("NewMusicManager failed.")
}
if mm.Len() != 0 {
t.Error("NewMusicManager failed, not empty.")
}
m0 := &MusicEntry{
"1", "My Heart Will Go On", "Celion Dion", "http://xxxxxxxxx", "MP3"}
mm.Add(m0)
if mm.Len() != 1 {
t.Error("MusicManager.Add() failed.")
}
m := mm.Find(m0.Name)
if m == nil {
t.Error("MusicManager.Find() failed.")
}
if m.Id != m0.Id || m.Artist != m0.Artist || m.Name != m0.Name || m.Source != m0.Source || m.Type != m0.Type {
t.Error("MusicManager.Find() failed. Found item mismatch.")
}
m, err := mm.Get(0)
if m == nil {
t.Error("MusicManager.Get() failed.", err)
}
m = mm.Remove("My Heart Will Go On")
if m == nil || mm.Len() != 0 {
t.Error("MusicManager.Remove() failed.", err)
}
}
MP3.go
package tool
import (
"fmt"
"time"
)
type MP3Player struct {
stat int
progress int
}
func (p *MP3Player)Play(source string) {
fmt.Println("Playing MP3 music", source)
p.progress = 0
for p.progress < 100 {
time.Sleep(100 * time.Millisecond) // 假装正在播放
fmt.Print(".")
p.progress += 10
}
fmt.Println("nFinished playing", source)
}
play.go
package tool
import "fmt"
type Player interface {
Play(source string)
}
func Play(source, mtype string) {
var p Player
switch mtype {
case "MP3":p = &MP3Player{}
default:
fmt.Println("Unsupported music type", mtype)
return
}
p.Play(source)
}
