根据 method 属性将接口绑定到 ninject 中的 2 个不同的具体对象

Question

我有 2 个不同的具体对象，让我们保存 ConcreteOne 和 ConcreteTwo。其中每一个都实现一个接口ILooseyGoosey。我希望 ninject 根据该方法的属性调用不同的方法。

这是我到目前为止所拥有的：

public class ConcreteOne : ILooseyGoosey
{
  public void SomeMethod() { };
}
public class ConcreteTwo : ILooseyGoosey
{
  public void SomeMethod() { } ;
}
public interface ILooseyGoosey
{
  [CallConcreteTwo()]
  void SomeMethod();
}

这是我在 Ninject 模块中定义的：

public override void Load()
{
  Bind<ILooseyGoosey>().To<ConcreteOne>().InjectMethodsWhere(mi => mi.GetCustomAttributes(true).Where(a => a.GetType() == typeof(CallConcreteTwoAttribute)).Count() == 0);
  Bind<ILooseyGoosey>().To<ConcreteTwo>().InjectMethodsWhere(mi => mi.GetCustomAttributes(true).Where(a => a.GetType() == typeof(CallConcreteTwoAttribute)).Count() > 0);
}

我收到以下错误：

System.NotSupportedException：注册服务时出错 ILooseyGoosey：为服务声明了多个默认绑定。 找到 2 个默认绑定：

Answer 1

问题在于您将一个接口分配给两个实现，而没有任何条件逻辑。您应用的逻辑仅适用于注入的方法。 Ninject 不知道要使用哪个绑定，因为您表明它们都是默认的。

Answer 2

不确定您是否仍然需要答案，基于元数据的方法是正确的选择。您希望在 Ninject 2.0 中以元数据方式进行绑定。请参阅与 Ninject 2.0 的上下文绑定

Answer 3

不是我写的。请参阅：http://www.ninject.org/wiki.html

Ninject
Download it Extensions Contribute Visit the Dojo Speak up Sponsors Merchandise

Version:  
»Ninject
»MVC3
Multi injectionEdit PagePage History
Ninject allows you to inject multiple objects bound to a particular type or interface. For example, if we have our IWeapon interface, and two implementations, Sword and Dagger:

public interface IWeapon
{
    string Hit(string target);
}

public class Sword : IWeapon 
{
    public string Hit(string target) 
    {
        return "Slice " + target + " in half";
    }
}

public class Dagger : IWeapon 
{
    public string Hit(string target) 
    {
        return "Stab " + target + " to death";
    }
}
Here we have the Samurai class. You can see that its constructor takes an array of IWeapon.

public class Samurai 
{
    readonly IEnumerable allWeapons;
    public Samurai(IWeapon[] allWeapons) 
    {
        this.allWeapons = allWeapons;
    }

    public void Attack(string target) 
    {
        foreach (IWeapon weapon in this.allWeapons)
            Console.WriteLine(weapon.Hit(target));
    }
}
We can create bindings from the IWeapon interface to the Sword and Dagger types.

class TestModule : Ninject.Modules.NinjectModule
{
    public override void Load()
    {
        Bind().To();
        Bind().To();
    }
}
Finally, a kernel is created with the module we defined above. We ask Ninject for an instance of a Samurai. Now, when you ask the Samurai to attack, you will see it has been given an array of all the types bound to IWeapon.

class Program
{
    public static void Main() 
    {
        Ninject.IKernel kernel = new StandardKernel(new TestModule());

        var samurai = kernel.Get();
        samurai.Attack("your enemy");
    }
}
And you’ll see:

Stab your enemy to death
Slice your enemy in half
The kernel also exposes a GetAll method which lets you generate the same output by doing:

class Program
{
    public static void Main() 
    {
        Ninject.IKernel kernel = new StandardKernel(new TestModule());

        IEnumerable weapons = kernel.GetAll();
        foreach(var weapon in weapons)
            Console.WriteLine(weapon.Hit("the evildoers"));
    }
}
Continue reading: Object Scopes

Enkari
Ninject is the illegitimate brainchild of Nate Kohari. Copyright ©2007-2012 Enkari, Ltd and the Ninject project contributors.