设计模式深度剖析：适配器模式在Go语言中的实践

运维开发王义杰

发布于 2023-08-10 16:59:45

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发布于 2023-08-10 16:59:45

文章被收录于专栏：运维开发王义杰运维开发王义杰

设计模式是为我们解决一类特定问题的时间证明的解决方案。本文将详细介绍一种特别的设计模式——适配器模式(Adapter Pattern)，并且通过一个Go语言的例子来演示其在实际问题中的应用。

适配器模式简介

适配器模式是一种结构型设计模式，它允许将一个已存在的类的接口转换成客户端期望的另一个接口。它能帮助我们实现两个相关或者依赖的接口间的互通。在许多现实场景中，适配器模式都得到了广泛的应用，例如，电源适配器、数据格式转换等。

Go中的适配器模式

下面我们将通过Go语言的代码例子，来详细说明如何在Go语言中实现适配器模式。

在这个例子中，我们有两个接口：MusicPlayer和AdvancedMusicPlayer。MusicPlayer接口有一个方法playAudio，而AdvancedMusicPlayer接口有两个方法：playVlc和playMp4。

type MusicPlayer interface {
  PlayAudio(audioType string, filename string)
}

type AdvancedMusicPlayer interface {
  PlayVlc(filename string)
  PlayMp4(filename string)
}

然后我们有两个实现AdvancedMusicPlayer接口的具体类：VlcPlayer和Mp4Player。

type VlcPlayer struct{}

func (v *VlcPlayer) PlayVlc(filename string) {
  fmt.Printf("Playing vlc file. Name: %s\n", filename)
}

func (v *VlcPlayer) PlayMp4(filename string) {
  // Do nothing
}

type Mp4Player struct{}

func (m *Mp4Player) PlayVlc(filename string) {
  // Do nothing
}

func (m *Mp4Player) PlayMp4(filename string) {
  fmt.Printf("Playing mp4 file. Name: %s\n", filename)
}

然后我们创建了一个适配器类MediaAdapter，实现了MusicPlayer接口，并在内部维护了一个AdvancedMusicPlayer接口的实例。

type MediaAdapter struct {
  advancedMusicPlayer AdvancedMusicPlayer
}

func NewMediaAdapter(audioType string) *MediaAdapter {
  mediaAdapter := &MediaAdapter{}

  if audioType == "vlc" {
    mediaAdapter.advancedMusicPlayer = &VlcPlayer{}
  } else if audioType == "mp4" {
    mediaAdapter.advancedMusicPlayer = &Mp4Player{}
  }

  return mediaAdapter
}

func (m *MediaAdapter) PlayAudio(audioType string, filename string) {
  if audioType == "vlc" {
    m.advancedMusicPlayer.PlayVlc(filename)
  } else if audioType == "mp4" {
    m.advancedMusicPlayer.PlayMp4(filename)
  }
}

最后，我们创建了一个AudioPlayer类，也实现了MusicPlayer接口。在AudioPlayer类中，我们会根据不同的音频类型，使用MediaAdapter来播放音频。

type AudioPlayer struct{}

func (a *AudioPlayer) PlayAudio(audioType string, filename string) {
  if audioType == "mp3" {
    fmt.Printf("Playing mp3 file. Name: %s\n", filename)
  } else if audioType == "vlc" || audioType == "mp4" {
    mediaAdapter := NewMediaAdapter(audioType)
    mediaAdapter.PlayAudio(audioType, filename)
  }
}

这样，我们就能够使用AudioPlayer类来播放不同类型的音频文件了，而且如果我们想要支持更多类型的音频文件，我们只需要创建相应的播放器类和适配器类就可以了。

完整代码

package main

import (
  "fmt"
)

// 定义接口
type MusicPlayer interface {
  PlayAudio(audioType string, filename string)
}

type AdvancedMusicPlayer interface {
  PlayVlc(filename string)
  PlayMp4(filename string)
}

// 实现接口的具体类
type VlcPlayer struct{}

func (v *VlcPlayer) PlayVlc(filename string) {
  fmt.Printf("Playing vlc file. Name: %s\n", filename)
}

func (v *VlcPlayer) PlayMp4(filename string) {
  // Do nothing
}

type Mp4Player struct{}

func (m *Mp4Player) PlayVlc(filename string) {
  // Do nothing
}

func (m *Mp4Player) PlayMp4(filename string) {
  fmt.Printf("Playing mp4 file. Name: %s\n", filename)
}

// 适配器类
type MediaAdapter struct {
  advancedMusicPlayer AdvancedMusicPlayer
}

func NewMediaAdapter(audioType string) *MediaAdapter {
  mediaAdapter := &MediaAdapter{}

  if audioType == "vlc" {
    mediaAdapter.advancedMusicPlayer = &VlcPlayer{}
  } else if audioType == "mp4" {
    mediaAdapter.advancedMusicPlayer = &Mp4Player{}
  }

  return mediaAdapter
}

func (m *MediaAdapter) PlayAudio(audioType string, filename string) {
  if audioType == "vlc" {
    m.advancedMusicPlayer.PlayVlc(filename)
  } else if audioType == "mp4" {
    m.advancedMusicPlayer.PlayMp4(filename)
  }
}

// 最终的音乐播放器
type AudioPlayer struct{}

func (a *AudioPlayer) PlayAudio(audioType string, filename string) {
  if audioType == "mp3" {
    fmt.Printf("Playing mp3 file. Name: %s\n", filename)
  } else if audioType == "vlc" || audioType == "mp4" {
    mediaAdapter := NewMediaAdapter(audioType)
    mediaAdapter.PlayAudio(audioType, filename)
  }
}

func main() {
  player := &AudioPlayer{}

  player.PlayAudio("mp3", "beyond_the_horizon.mp3")
  player.PlayAudio("mp4", "alone.mp4")
  player.PlayAudio("vlc", "far_far_away.vlc")
  player.PlayAudio("avi", "mind_me.avi") // unsupported format
}