go示例2：模擬音樂播放器

manager.go

package mlib

import "errors"

type MusicEntry struct {
	Id     string
	Name   string
	Genre  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(index int) *MusicEntry {
	if index < 0 || index >= len(m.musics) {
		return nil
	}

	removedMusic := &m.musics[index]

	m.musics = append(m.musics[:index], m.musics[index+1:]...)

	return removedMusic
}

manager_test.go

package mlib

import "testing"

func TestOps(t *testing.T) {
	mm := NewMusicManager()
	if mm == nil {
		t.Error("NewMusicManager failed, not empty")
	}
	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.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)
	}
}

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)
		fmt.Print(".")
		p.progress += 10
	}

	fmt.Println("\nFinished playing", source)
}

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)
}

mplayer.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"

	"mlib"
	"mp"
)

var lib *mlib.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) == 7 {
				id++
				lib.Add(&mlib.MusicEntry{strconv.Itoa(id),
					tokens[2], tokens[3], tokens[4], tokens[5], tokens[6]})
			} else {
				fmt.Println("USAGE: lib add <name><artist><source><type>")
			}
		}
	case "remove":
		if len(tokens) == 3 {
			index, err := strconv.Atoi(tokens[2])
			if err != nil {
				fmt.Println("USAGE: lib remvoe <index>")
			} else {
				lib.Remove(index)
			}
		} else {
			fmt.Println("USAGE: lib remove <index>")
		}
	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 exit.")
	}

	mp.Play(e.Source, e.Type)
}

func main() {
	fmt.Println(`
			Enter folloing 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 = mlib.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])
		}
	}
}