Question

我阅读了以下文章.NET Junkie - Meanwhile... on the command side of my architecture，该文章由另一个stackoverflow用户建议，该用户概述了命令模式，并提供了如何在文章末尾使用DI的策略。

这有很大的帮助但是我缺少的一件事，就是说我创建了一个名为CheckoutCustomerCommandHandler的新类。

现在，假设我需要通过构造函数将此命令和MoveCustomerCommandHandler注入控制器。这对DI容器设置和构造函数有何影响？

核心是，它们都实现了相同的界面。这似乎会导致DI容器的查找问题。在文章示例中，这是他们的示例进样器设置：

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

// Exactly the same as before, but now with the interface.
public class MoveCustomerCommandHandler
: ICommandHandler<MoveCustomerCommand>
{
    private readonly UnitOfWork db;

    public MoveCustomerCommandHandler(UnitOfWork db,
    [Other dependencies here])
    {
        this.db = db;
    }

    public void Handle(MoveCustomerCommand command)
    {
        // TODO: Logic here
    }
}

// Again, same implementation as before, but now we depend
// upon the ICommandHandler abstraction.
public class CustomerController : Controller
{
    private ICommandHandler<MoveCustomerCommand> handler;

    public CustomerController(
    ICommandHandler<MoveCustomerCommand> handler)
    {
        this.handler = handler;
    }

    public void MoveCustomer(int customerId, 
        Address newAddress)
    {
        var command = new MoveCustomerCommand
        {
            CustomerId = customerId,
            NewAddress = newAddress
        };

        this.handler.Handle(command);
    }
}

using SimpleInjector;
using SimpleInjector.Extensions;

var container = new Container();

// Go look in all assemblies and register all implementations
// of ICommandHandler<T> by their closed interface:
container.RegisterManyForOpenGeneric(
    typeof(ICommandHandler<>),
    AppDomain.CurrentDomain.GetAssemblies());

// Decorate each returned ICommandHandler<T> object with
// a TransactionCommandHandlerDecorator<T>.
container.RegisterDecorator(typeof(ICommandHandler<>),
    typeof(TransactionCommandHandlerDecorator<>));

// Decorate each returned ICommandHandler<T> object with
// a DeadlockRetryCommandHandlerDecorator<T>.
container.RegisterDecorator(typeof(ICommandHandler<>),
    typeof(DeadlockRetryCommandHandlerDecorator<>));

Answer 1

这是你的类声明的样子......

public class CheckoutCustomerCommandHandler :
    ICommandHandler<CheckoutCustomerCommand> {...}

public class MoveCustomerCommandHandler : 
    ICommandHandler<MoveCustomerCommand> {...}

这些看起来可能实现了相同的接口，但实际上它们编译为两个不同的接口，因为泛型参数不同。您的DI框架将能够区分它们。

命令模式使用依赖注入为MVC 3控制器

1 个答案: