Autofac IComponentContext.Resolve 带参数

Question

如何向类型注册提供 IComponentContext 函数，其中参数可以是类型（待解析）或传入的参数？

因此，如果我有一个函数，我想将其用于注册，例如：

    public static ClassTarget Resolver(ClassArg1 arg1, ClassArg2 arg2)
    {
        // Do something fancier than this...
        return new ClassTarget(arg1, arg2);
    }

如何为 ClassTarget 注册？

一个完整的例子，我目前正在使用的 hack 和有效的备用注册（正如人们所期望的那样）：

public class ClassArg1 { }

public class ClassArg2 { }

public class ClassTarget
{
    public ClassTarget(ClassArg1 arg1, ClassArg2 arg2) {  }
}

public static class ResolveFuncTest
{
    public static ClassTarget Resolver(ClassArg1 arg1, ClassArg2 arg2)
    {
        // Do something fancier than this...
        return new ClassTarget(arg1, arg2);
    }

    private static T GetArgValue<T>(IComponentContext componentContext, IEnumerable<Parameter> parameters)
    {
        if (parameters != null)
        {
            var param = parameters.OfType<TypedParameter>().FirstOrDefault(p => p.Type == typeof(T));
            if (param != null)
            {
                return (T)param.Value;
            }
        }

        return componentContext.Resolve<T>();
    }

    public static void Test()
    {
        var builder = new ContainerBuilder();

        // The first argument will be resolved as normal
        builder.RegisterType<ClassArg1>().AsSelf().SingleInstance();

        // Works - just a typical type registration without the Func used
        //builder.RegisterType<ClassTarget>().AsSelf().SingleInstance();
        // Works - but only if we know how to resolve the arguments as types or parameters
        //builder.Register((c, p) => Resolver(c.Resolve<ClassArg1>(), p.TypedAs<ClassArg2>())).AsSelf().SingleInstance();
        // Works - smells though!
        builder.Register((c, p) => Resolver(GetArgValue<ClassArg1>(c,p), GetArgValue<ClassArg2>(c, p))).AsSelf().SingleInstance();

        // Build/scope
        var context = builder.Build();
        var scope = context.BeginLifetimeScope();

        // The second argument is passed as an instance/parameter at resolve time
        scope.Resolve<ClassTarget>(new TypedParameter(typeof(ClassArg2), new ClassArg2()));
    }
}

很明显，我误解了这里的核心内容，因为我正在为自己做 Autofac 通常无缝执行的参数解析而跌跌撞撞！ Resolve 我在文档中遗漏了另一个重载吗？

Answer 1

如果您必须完全在 Resolver 函数内进行初始化，您可能无法使用现有的机制。 也就是说，如果您有一个特定功能，并且无论出于何种原因，您都必须实例化 ClassTarget 对象并且您必须在那里初始化它，您被卡住了。

如果你能稍微重构一下，你可以利用 Autofac 的 delegate factories 特性。

这里有一个代码示例，说明如果您稍作重构并使用委托工厂功能，代码可能会是什么样子：

public class ClassArg1 { }

public class ClassArg2 { }

public class ClassTarget
{
  // Create a delegate factory with the set of parameters you require
  // during the Resolve operation - things that won't be auto-filled by Autofac.
  public delegate ClassTarget Factory(ClassArg2 arg2);

  // The constructor can have all the required parameters. Make sure the
  // names here match the names in the delegate factory.
  public ClassTarget(ClassArg1 arg1, ClassArg2 arg2)  { }

  // Just something to show the initalization working.
  public bool IsInitialized { get; set; }
}

public static class ResolveFuncTest
{
  public static void Initialize(ClassTarget target)
  {
    // Instead of newing up the ClassTarget here, let Autofac do that
    // through the delegate factory and *only* do initialization here -
    // the "something fancier" you previously alluded to.
    target.IsInitialized = true;
  }

  public static void Test()
  {
    // Register the argument that gets populated by Autofac.
    var builder = new ContainerBuilder();
    builder.RegisterType<ClassArg1>().AsSelf().SingleInstance();

    // Register the ClassTarget and Autofac will see the factory delegate.
    builder.RegisterType<ClassTarget>().OnActivated(args => Initialize(args.Instance));

    var context = builder.Build();
    using(var scope = context.BeginLifetimeScope())
    {
      // Resolve a factory delegate rather than resolving the class directly.
      var factory = scope.Resolve<ClassTarget.Factory>();
      var classTarget = factory(new ClassArg2());

      // Do whatever you need.
      Console.WriteLine("ClassTarget is initialized? {0}", classTarget.IsInitialized);
    }
  }
}

我猜这更接近您希望实现的目标。

Autofac IComponentContext.Resolve 带参数

Autofac IComponentContext.Resolve With Parameters

c#

inversion-of-control

autofac