c# - autofac 中的工厂模式

Question

我想在 Autofac 中实现工厂模式。这是在 Ninject 中完成的:

Bind<ICarFilter>().To<CarFilter >();
Bind<IBikeFilter>().To<BikeFilter>();
Bind<IFilterFacade>().ToFactory().InSingletonScope();

这是 IFilterFacade 的定义

public interface IFilterFacade
    {    
        ICarFilter CreateCarFilter();

        IBikeFIlter CreateBikeFilter();         
    }

如果我想要一个 CarFilter 类型的实例，我需要做的就是:

public class HomeController(IFilterFacade filterFacade)
{
    FilterFacade = filterFacade;
}

public IFilterFacade FilterFacade { get;set; }

public ActionResult Index()
{
  var bikeFilter = FilterFacade.CreateBikeFilter();
}

关于如何在 AutoFac 中执行此操作的任何示例。我检查了 AutoFac 文档，但找不到答案或示例。

Answer 1

Autofac 中没有 ToFactory 的等效项，但您可以轻松实现通用工厂等效项。

public interface IFilterFactory
{
    TFilter Get() where TFilter : IFilter; 
}

public class FilterFactory : IFilterFactory
{

    public FilterFactory(ILifetimeScope scope)
    {
        this._scope = scope; 
    }

    private readonly ILifetimeScope _scope; 

    public TFilter Get<TFilter>()
    {
        return this._scope.Resolve<TFilter>(); 
    }
}

然后像这样注册它:

builder.RegisterType<FilterFactory>().As<IFilterFactory>(); 
builder.RegisterType<BikeFilter>().As<IBikeFilter>(); 
builder.RegisterType<CarFilter>().As<ICarFilter>(); 

并以这种方式使用它

public class HomeController
{ 
    private readonly IFilterFactory _filters;

    public HomeController(IFilterFactory filters)
    {
        this._filters = filters; 
    }

    public ActionResult Index()
    {
        var bikeFilter = this._filters.Get<IBikeFilter>();
        // ...
    }
}

我将 Create 方法重命名为 Get，因为该方法将在生命周期范围内查找一个实例，并仅在需要时创建一个实例。

另一种可能的解决方案是使用 Named and Keyed Service和内置的 IIndex 类型。

builder.RegisterType<BikeFilter>().Named<IFilter>("Bike"); 
builder.RegisterType<CarFilter>().Named<IFilter>("Car");

然后在你的 Controller 上

public class HomeController
{ 
    private readonly IIndex<String, IFilter> _filters;

    public HomeController(IIndex<String, IFilter> filters)
    {
        this._filters = filters; 
    }

    public ActionResult Index()
    {
        var bikeFilter = this._filters["Bike"];
        // ...
    }
}