Unity用法（属性注入的两种方法）
对象之间的依赖关系有时还表现为通过属性来引入的方式，同样也可以用IOC的Property (Setter) Injection 方式来解耦。
什么情况下使用Property (Setter) Injection
当实例化父对象时也能自动实例化所依赖的对象
通过简单的方式使得很容易做到在代码中查看每个类所依赖的项
父对象有很多相互之间有关联关系的构造器，导致在调试和维护时很不方便。
父对象包含有很多参数构造器，特别是参数类型相似的只能通过参数的位置来辨别的
让用户(将调用这些代码的程序)更方便的看到有哪些对象可以用，这在Constructor Injection里是没办法实现的。
通过修改依赖对象的代码来控制哪些对象可以被注入，而不用改动父对象或应用程序
配置文件方式：
现假设有如下对象
public class WmaPlayer : IPlayer
{
public void Play()
{
this.WmaSong.Name = "xxx";
this.WmaSong.Singer = "yyy";
Console.WriteLine(string.Format("Now Playing [{0}] Singing by ({1})", this.WmaSong.Name, this.WmaSong.Singer));
}
public Song WmaSong
{
get;
set;
}
}
在配置文件中添加如下配置
<register type="IPlayer"
mapTo="SongPlayerLib.WmaPlayer,
SongPlayerLib" name="WmaPlayer">
<property name="WmaSong" dependencyType="Song"/>
</register >
其中dependencyType="Song" 的Song可以在
<typeAlias alias="Song"
type="SongPlayerLib.Song,
SongPlayerLib" /> 中配置别名。
如果对同一个IPlayer接口的map有多个配置 。
如：
<register type="IPlayer"
mapTo="SongPlayerLib.Mp3Player,
SongPlayerLib">
那么可以通过以下方式来得到对应的类型实例
IPlayer player = container.Resolve<IPlayer>("WmaPlayer");
这样就得到是WmaPlayer实例。
代码方式：
假设有如下类定义：
//歌曲类
public class Song
{
//歌手
public string Singer
{
get
{
return "Westlife";
}
}
//歌曲名
public string Name
{
get
{
return "My Love";
}
}
}
public abstract class Player
{
[Dependency]
public Song Song { get ; set ; }
public abstract string Name { get ; }
public void Play()
{
Console.WriteLine( string .Format( " {0}: Now Playing [{1}] Singing by ({2}) " , this .Name, this .Song.Name, this .Song.Singer));
}
}
public class Mp3Player : Player
{
public override string Name
{
get
{
return " Mp3 Player " ;
}
}
}
public class CDPlayer : Player
{
public override string Name
{
get
{
return " CD Player " ;
}
}
}
public class Song
{
//歌手
public string Singer
{
get
{
return "Westlife";
}
}
//歌曲名
public string Name
{
get
{
return "My Love";
}
}
}
public abstract class Player
{
[Dependency]
public Song Song { get ; set ; }
public abstract string Name { get ; }
public void Play()
{
Console.WriteLine( string .Format( " {0}: Now Playing [{1}] Singing by ({2}) " , this .Name, this .Song.Name, this .Song.Singer));
}
}
public class Mp3Player : Player
{
public override string Name
{
get
{
return " Mp3 Player " ;
}
}
}
public class CDPlayer : Player
{
public override string Name
{
get
{
return " CD Player " ;
}
}
}
开始
通过为类的属性贴上[Dependency]标签，使得Unity容器在获取类对象实例时，自动实例化该属性所依赖的对象，并注入到属性中。
看一个例子，Mp3Player类有一个Song属性，它被贴上[Dependency]标签。
[Dependency]
public Song Song { get ; set ; }
public Song Song { get ; set ; }
可以通过下面的方式来获取Mp3Player对象实例：
IUnityContainer container
=
new
UnityContainer();
container.RegisterType < Player, Mp3Player > ();
Player player = container.Resolve < Player > ();
container.RegisterType < Player, Mp3Player > ();
Player player = container.Resolve < Player > ();
player.Play();
这里通过为Mp3Player类的Song属性贴上[Dependency]标签，来表示Unity容器装载对象时将自动实例化Song对象，然后注入到Mp3Player的Song属性里。从输出结果可以看出，容器在装配Mp3Player对象时自动装载有加上[Dependency]标签的所依赖的属性对象。
还可以为[Dependency]特性指定Name，再看一个例子：
这是一个播放器商店类，为PopularPlayer属性贴上[Dependency]标签，同时指定Name为"Mp3Player"。
//播放器商店
public class PlayerStore
{
// 最受欢迎的播放器类型(Mp3Player、CDPlayer
)
[Dependency("Mp3Player")]
public Player PopularPlayer { get ; set ; }
}
public class PlayerStore
{
// 最受欢迎的播放器类型(Mp3Player、CDPlayer
)
[Dependency("Mp3Player")]
public Player PopularPlayer { get ; set ; }
}
在Unity容器中为Player基类注册两个映射( Mp3Player 和 CDPlayer ), 分别指定映射的Name。可以通过下面的方式来获取PlayerStore对象实例,并输出该店最受欢迎的播放器名：
IUnityContainer container
=
new
UnityContainer();
container.RegisterType < Player, Mp3Player > ( " Mp3Player " );
container.RegisterType < Player, CDPlayer > ( " CDPlayer " );
PlayerStore player = container.Resolve < PlayerStore > ();
container.RegisterType < Player, Mp3Player > ( " Mp3Player " );
container.RegisterType < Player, CDPlayer > ( " CDPlayer " );
PlayerStore player = container.Resolve < PlayerStore > ();
Console.WriteLine(player.PopularPlayer.Name);
