c# - 如何获取在 Unity 中注入(inject)的对象的类型？

Question

我有一个类型在其构造函数中接收另一个类型，通常是创建它的对象的类型，例如:

public class Logger {
    public Logger(Type parent) { ... }
}

我想指示 Unity 解析 Logger 将需要它的对象的类型作为参数传递给其构造函数。像这样的东西:

// ... would be some directive to tell Unity to use the type that
/// depends on Logger
container.RegisterType<Logger>(new InjectionConstructor(...));

所以当我尝试解析 MyService 时:

public MyService {
    public MyService(Logger logger) { ... }
}

它将返回:

var logger = new Logger(typeof(MyService));
return new MyService(logger);

这可能吗？还有其他方法吗？

Answer 1

实际上，你可以这样做:

internal class Program
{
    static void Main( string[] args )
    {
        var container = new UnityContainer();
        container.RegisterType<IInterface, Implementation>( new MyInjectionConstructor() );

        // this instance will get a logger constructed with loggedType == typeof( Implementation )
        var instance = container.Resolve<IInterface>();
    }
}

internal class MyInjectionConstructor : InjectionMember
{
    public override void AddPolicies( Type serviceType, Type implementationType, string name, IPolicyList policies )
    {
        policies.Set<IConstructorSelectorPolicy>( new MyConstructorSelectorPolicy(), new NamedTypeBuildKey( implementationType, name ) );
    }
}

internal class MyConstructorSelectorPolicy : DefaultUnityConstructorSelectorPolicy
{
    protected override IDependencyResolverPolicy CreateResolver( ParameterInfo parameter )
    {
        if( parameter.ParameterType == typeof( ILogger ) )
        {
            return new LiteralValueDependencyResolverPolicy( new Logger( parameter.Member.DeclaringType ) );
        }
        return base.CreateResolver( parameter );
    }
}

internal interface ILogger
{
}

internal class Logger : ILogger
{
    public Logger( Type loggedType )
    {
    }
}

internal interface IInterface
{
}

internal class Implementation : IInterface
{
    public Implementation( ILogger logger )
    {
    }
}

这只是概念代码的证明，在生产使用之前可能需要稍微改进一下......