c# - Ninject 的装饰器模式

Question

我正在尝试申请 this制作验证包装器的方法。我创建了以下接口(interface)，我使用 Ninject 作为我的 DI 容器

public interface ICommandHandler<TCommand>
    {
        void Handle(TCommand command);
    }

public interface IValidator<T>
{
    IEnumerable<ValidationResult> Validate(T command);
}

public class ValidationCommandHandlerDecorator<T>:ICommandHandler<T>
{
    private readonly ICommandHandler<T> _decoratee;
    private readonly IValidator<T> _validator;

    public ValidationCommandHandlerDecorator(ICommandHandler<T> decoratee,IValidator<T> validator )
    {
        _decoratee = decoratee;
        _validator = validator;
    }
    public void Handle(T command)
    {
        this._validator.Validate(command);
        this._decoratee.Handle(command);
    }
}

public class SaveNewOsiRequestController : ApiController
{
    private readonly ICommandHandler<OsiRequest> _osiRequestSaveHandler;

    public SaveNewOsiRequestController(ICommandHandler<OsiRequest> osiRequestSaveHandler)
    {
        _osiRequestSaveHandler = osiRequestSaveHandler;
    }
}

下面是我将具体类注入(inject) Controller 的方式:

        kernel.Bind(typeof (IValidator<>)).To(typeof (OsiRequestValidator));

        kernel.Bind(typeof (ICommandHandler<>))
            .To(typeof (SaveOsiRequestCommandHandler))
            .WhenInjectedInto(typeof (ValidationCommandHandlerDecorator<>));

        kernel.Bind(typeof (ICommandHandler<>))
            .To(typeof (ValidationCommandHandlerDecorator<>))
            .WhenInjectedInto(typeof(SaveNewOsiRequestController));

代码运行良好，没有任何问题。然而问题是我怎样才能用 Ninject 为另一个 Controller 做同样的注入(inject)？为了简单起见，我想像这样将另一个 Validator 和另一个 CommandHandler 注入(inject)到另一个 Controller 中:

        kernel.Bind(typeof (IValidator<>)).To(typeof (ANOTHER_Validator));

        kernel.Bind(typeof (ICommandHandler<>))
            .To(typeof (ANOTHER_CommandHandler))
            .WhenInjectedInto(typeof (ValidationCommandHandlerDecorator<>));

        kernel.Bind(typeof (ICommandHandler<>))
            .To(typeof (ValidationCommandHandlerDecorator<>))
            .WhenInjectedInto(typeof(ANOTHER_RequestController));

Answer 1

这里的问题是您正在执行通用绑定(bind)，但您是在特定情况下使用它。只有当您希望泛型绑定(bind)适用于该绑定(bind)的所有情况(或至少是您可以有条件地绑定(bind)到的所有情况)时，您才想使用泛型绑定(bind)。

为此，您可以轻松地做到这一点:

kernel.Bind<IValidator<OsiRequest>>().To<OsiRequestValidator>();

kernel.Bind<ICommandHandler<OsiRequest>()
        .To<SaveOsiRequestCommandHandler>()
        .WhenInjectedInto<ValidationCommandHandlerDecorator<OsiRequest>>();

kernel.Bind<ICommandHandler<OsiRequest>()
        .To<ValidationCommandHandlerDecorator<OsiRequest>()
        .WhenInjectedInto<SaveNewOsiRequestController>();

那么每增加一个就是:

kernel.Bind<IValidator<DifferentRequest>>().To<DifferentValidator>();

kernel.Bind<ICommandHandler<DifferentRequest>()
        .To<DifferentRequestCommandHandler>()
        .WhenInjectedInto<ValidationCommandHandlerDecorator<DifferentRequest>>();

kernel.Bind<ICommandHandler<DifferentRequest>()
        .To<ValidationCommandHandlerDecorator<DifferentRequest>()
        .WhenInjectedInto<DifferentRequestController>();

您可以更改最后一个绑定(bind)，这样您就不必为每种类型声明它:

kernel.Bind(typeof (ICommandHandler<>))
        .To(typeof (ValidationCommandHandlerDecorator<>))
        .WhenInjectedInto<ApiController>();