type Music struct {
Id string
Name string
Artist string
Source string
Type string
}
然後開始實現這個音樂庫管理型別，其中我們使用了一個陣列切片作為基礎儲存結構，其他的操作其實都只是對這個陣列切片的包裝，程式碼如下所示。//manager.go
package library
import "errors"
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(index int) *MusicEntry {
if index < 0 || index >= len(m.musics) {
return nil
}
removedMusic := &m.musics[index]
// 從陣列切片中刪除元素
if index < len(m.musics)-1 { // 中間元素
m.musics = append(m.musics[:index-1], m.musics[index+1:]...)
} elseif index == 0 { // 刪除僅有的一個元素
m.musics = make([]MusicEntry, 0)
} else { // 刪除的是最後一個元素
m.musics = m.musics[:index-1]
}
return removedMusic
}
實現了這麼重要的一個基礎資料管理模組後，我們應該馬上編寫單元測試，而不是給自己藉口說等將來有空的時候再補上。下面的程式碼實現了 MusicManager 型別的單元測試。//manager_test.go
package library
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", Pop,
"http://qbox.me/24501234", 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.Genre != m0.Genre ||
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(0)
if m == nil || mm.Len() != 0 {
t.Error("MusicManager.Remove() failed.", err)
}
}
這個單元測試看起來似乎有些偷懶，但它基本上已經覆蓋了 MusicManager 的所有功能，實際上也確實測出了 MusicManager 實現過程中的幾個問題。因此，養成良好的單元測試習慣還是非常有價值的。func Play(source, mtype string)
這裡沒有直接將 MusicEntry 作為引數傳入，這是因為 MusicEntry 包含了一些多餘的資訊。本著最小原則，我們只需要將真正需要的資訊傳入即可，即音樂檔案的位置以及音樂的型別。
type Player interface {
Play(source string)
}
//play.go
package mp
import "fmt"
type Player interface {
Play(source string)
}
func Play(source, mtype string) {
var p Player
switch mtype {
case "MP3":
p = &MP3Player{}
case "WAV":
p = &WAVPlayer{}
default:
fmt.Println("Unsupported music type", mtype)
return
}
p.Play(source)
}
因為我們這個例子並不會真正實現多媒體檔案的解碼和播放過程，所以對於 MP3Player 和 WAVPlayer，我們只實現其中一個作為範例，程式碼如下所示。//mp3.go
package mp
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) // 假裝正在播放
fmt.Print(".")
p.progress += 10
}
fmt.Println("nFinished playing", source)
}
當然，我們也應該對播放流程進行單元測試。因為單元測試比較簡單，這裡就不再列出完整的單元測試程式碼了。//mplayer.go
package main
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
"pkg/mplayer/mlib"
"pkg/mplayer/mp"
)
var lib *library.MusicManager
var id int = 1
var ctrl, signal chan int
func handleLibCommands(tokens []string) {
switch tokens[1] {
case "list":
for i := 0; i < lib.Len(); i++ {
e, _ := lib.Get(i)
fmt.Println(i+1, ":", e.Name, e.Artist, e.Source, e.Type)
}
case "add": {
if len(tokens) == 6 {
id++
lib.Add(&library.MusicEntry{strconv.Itoa(id),
tokens[2], tokens[3], tokens[4], tokens[5]})
} else {
fmt.Println("USAGE: lib add <name><artist><source><type>")
}
}
case "remove":
if len(tokens) == 3 {
lib.RemoveByName(tokens[2])
} else {
fmt.Println("USAGE: lib remove <name>")
}
default:
fmt.Println("Unrecognized lib command:", tokens[1])
}
}
func handlePlayCommand(tokens []string) {
if len(tokens) != 2 {
fmt.Println("USAGE: play <name>")
return
}
e := lib.Find(tokens[1])
if e == nil {
fmt.Println("The music", tokens[1], "does not exist.")
return
}
mp.Play(e.Source, e.Type, ctrl, signal)
}
func main() {
fmt.Println(`
Enter following commands to control the player:
lib list -- View the existing music lib
lib add <name><artist><source><type> -- Add a music to the music lib
lib remove <name> -- Remove the specified music from the lib
play <name> -- Play the specified music
`)
lib = library.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)
} elseif tokens[0] == "play" {
handlePlayCommand(tokens)
} else {
fmt.Println("Unrecognized command:", tokens[0])
}
}
}
$ go run mplayer.go
Enter following commands to control the player:
lib list -- View the existing music lib
lib add <name><artist><source><type> -- Add a music to the music lib
lib remove <name> -- Remove the specified music from the lib
play <name> -- Play the specified music
Enter command-> lib add HugeStone MJ ~/MusicLib/hs.mp3 MP3
Enter command-> play HugeStone
Playing MP3 music ~/MusicLib/hs.mp3
..........
Finished playing ~/MusicLib/hs.mp3
Enter command-> lib list
1 : HugeStone MJ ~/MusicLib/hs.mp3 MP3
Enter command-> lib view
Enter command-> q