Simple Injector：依赖于http请求的实现

Question

我是 Simple Injector 的初学者，有一个场景需要帮助来实现。我会尽量简化我需要做的事情。

我有一个 WebAPI，我需要在其中对用户进行身份验证，并根据用户类型选择一个实现。

考虑这个结构

public interface ICarRepository {
    void SaveCar(Car car);
}

//Some implementation for ICarRepository

public interface ICarLogic {
    void CreateCar(Car car);
}

public class CarLogicStandard: ICarLogic {
    private ICarRepository _carRepository;

    public CarLogicStandard(ICarRepository carRepository) {
        _carRepository = carRepository;
    }

    public void CreateCar(Car car) {
        car.Color = "Blue";
        _carRepository.SaveCar();
        //Other stuff...
    }
}

public class CarLogicPremium: ICarLogic {
    private ICarRepository _carRepository;

    public CarLogicPremium(ICarRepository carRepository) {
        _carRepository = carRepository;
    }

    public void CreateCar(Car car) {
        car.Color = "Red";
        _carRepository.SaveCar();
        //Other stuff 2...
    }

}

现在我有一个控制器

public class CarController: ApiController {
    private ICarLogic _carLogic;
    public CarController(ICarLogic carLogic) {
        _carLogic = carLogic;
    }

    public void Post(somePostData) {
        //Identify the user based on post data
        //....

        Car car = somePostData.SomeCar();
        _carLogic.CreateCar(car);
    }


}

上面的代码将不起作用，因为在我的请求中我需要识别用户。如果是高级用户，则控制器应使用 CarLogicPremium，如果是标准用户，则控制器应使用 CarLogicStandard。

我可以在 Global.asax 上配置不需要此逻辑的存储库和其他接口，但是，由于这种情况我需要请求来决定应该使用哪个实现，我想我需要解决这以其他方式。

有"Simple Injector"的方法来处理这个问题吗？还是我应该尝试另一种方法？

Answer 1

最简单的解决方案是在 composition root 中配置决策以及容器的其余配置：

protected void Application_Start()
{
    GlobalConfiguration.Configure(WebApiConfig.Register);

    var container = new Container();

    container.Register<CarLogicStandard>();
    container.Register<CarLogicPremium>();
    container.RegisterPerWebRequest<ICarRepository, CarRepository>();
    container.Register<ICarLogic>(
        () =>
            HttpContext.Current != null &&
                HttpContext.Current.User != null &&
                HttpContext.Current.User.IsInRole("Premium")
            ? (ICarLogic)container.GetInstance<CarLogicPremium>()
            : (ICarLogic)container.GetInstance<CarLogicStandard>()
        );

    // This is an extension method from the integration package.
    container.RegisterWebApiControllers(GlobalConfiguration.Configuration);

    container.Verify();

    GlobalConfiguration.Configuration.DependencyResolver =
        new SimpleInjectorWebApiDependencyResolver(container);
}

您还可以创建对当前用户的抽象，并使用高级功能

装饰标准功能

public class CarLogicPremium : ICarLogic
{
    private readonly ICarLogic decorated;
    private readonly ICurrentUser currentUser;
    private readonly ICarRepository carRepository;

    public CarLogicPremium(
        ICarLogic decorated,
        ICurrentUser currentUser,
        ICarRepository carRepository)
    {
        this.decorated = decorated;
        this.currentUser = currentUser;
        this.carRepository = carRepository;
    }

    public void CreateCar(Car car)
    {
        if (currentUser.IsPremiumMember)
        {
            car.Color = "Red";
            this.carRepository.SaveCar(car);
            //Other stuff 2...
        }
        else
        {
            this.decorated.CreateCar(car);
        }
    }
}

配置有点像这样

protected void Application_Start()
{
    GlobalConfiguration.Configure(WebApiConfig.Register);

    var container = new Container();

    container.Register<ICurrentUser, HttpCurrentUserProxy>();
    container.RegisterPerWebRequest<ICarRepository, CarRepository>();
    container.Register<ICarLogic, CarLogicStandard>();
    container.RegisterDecorator(typeof(ICarLogic), typeof(CarLogicPremium));

    container.RegisterWebApiControllers(GlobalConfiguration.Configuration);

    container.Verify();

    GlobalConfiguration.Configuration.DependencyResolver =
        new SimpleInjectorWebApiDependencyResolver(container);
}

但这实际上取决于您将随着时间的推移创建多少种服务变体。如果您将不断添加新的高级功能，您应该考虑实现 Try-X 模式的变体。让我知道以上其中一项是否适合您，或者您是否需要更多信息...

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