延迟/懒惰的决心

时间:2011-10-04 16:56:34

标签: castle-windsor lazy-evaluation resolve

给出以下代码:

public interface IMyContext
{
    string subtype { get; set; }
}

public class MyContext : IMyContext
{
    public string subtype { get; set; }
}

public interface IMyExporter
{
    string Export();
}

public class MyExporterXML : IMyExporter
{
    public string Export()
    {
        return "";
    }
}

public class MyExporterJson : IMyExporter
{
    public string Export()
    {
        return "";
    }
}

public class MyExporterFactory
{
    private IMyContext context;
    public MyExporterFactory(IMyContext context)
    {
        this.context = context;
    }

    public IMyExporter Create()
    {
        switch (context.subtype)
        {
            case "JSON" :
                    return new MyExporterJson();
            default:
                    return new MyExporterXML();
        }
    }
}

public class MyService
{
    private IMyContext context;
    private IMyExporter exporter;
    public MyService(IMyContext context, IMyExporter exporter)
    {
        this.context = context;
        this.exporter = exporter;
    }

    public string Extractdata()
    {
        return exporter.Export();
    }
}

[TestClass]
public class UnitTest2
{
    [TestMethod]
    public void TestMethod1()
    {
        var container = new WindsorContainer();
        container.Register(Component.For<IMyContext>().ImplementedBy<MyContext>());
        container.Register(Component.For<MyExporterFactory>());
        container.Register(Component.For<MyService>());
        container.Register(Component.For<IMyExporter>().UsingFactoryMethod(kernel => kernel.Resolve<MyExporterFactory>().Create()));
        var context = container.Resolve<IMyContext>();
        var service = container.Resolve<MyService>();

        context.subtype = "JSON";

        service.Extractdata();

    }
}

有没有办法让MyService中注入的导出器在实际使用时被解析? IE浏览器。运行上面的代码时,解析的导出器是MyExporterXML,但我真的希望它是MyExporterJson,因为context.subtype =“JSON”设置。但是,在设置子类型之前解析导出器...

我知道Castle :: Windsor有一个叫做委托工厂的东西,但我根本无法弄清楚如何使用它....

任何帮助将不胜感激,TIA

索伦

1 个答案:

答案 0 :(得分:3)

使用TypeFactoryFacility和自定义ITypedFactoryComponentSelector的组合。这是适用于您的情况。

首先,为工厂创建一个界面:

public interface IMyExporterFactory
{
    IMyExporter GetExporter(IMyContext context);
}

接下来,使用自定义工厂组件选择器,该选择器将使用上下文的子类型来确定组件名称(并更改注册以命名导出器):

public class ExporterComponentSelector : DefaultTypedFactoryComponentSelector
{
    protected override string GetComponentName(MethodInfo method, object[] arguments)
    {
        if (method.Name == "GetExporter")
        {
            var context = (IMyContext) arguments[0];
            return context.subtype;
        }

        return base.GetComponentName(method, arguments);
    }
}

以下是您的Windsor注册码的更新,其中包括TypedFactoryFacility和自定义选择器(并根据其子类型为您的出口商命名):

var container = new WindsorContainer();
container.AddFacility<TypedFactoryFacility>();
container.Register(
    Component.For<IMyExporterFactory>().AsFactory(c => c.SelectedWith(new ExporterComponentSelector())),
    Component.For<IMyExporter>().ImplementedBy<MyExporterJson>().Named("json"),
    Component.For<IMyExporter>().ImplementedBy<MyExporterXML>().Named("xml"),
    Component.For<IMyContext>().ImplementedBy<MyContext>(),
    Component.For<MyService>()
    );

现在您的服务只是收到一个IMyExporterFactory并使用它来解析导出器:

public class MyService
{
    private readonly IMyContext context;
    private readonly IMyExporterFactory exporterFactory;

    public MyService(IMyContext context, IMyExporterFactory exporterFactory)
    {
        this.context = context;
        this.exporterFactory = exporterFactory;
    }

    public string Extractdata()
    {
        var exporter = exporterFactory.GetExporter(context);
        return exporter.Export();
    }
}

您可能希望确保如果组件使用小写名称(“xml”,“json”)注册,则代码始终使用小写名称(或在ExporterComponentSelector中使用context.subtype.ToLower())。