Ninject 绑定通用接口

Question

这是

的跟进

答案是正确的，但我过于简化了代码。因为在接口上没有 out 参数，您不能将 TOrderRequest 作为 create 方法中的输入参数。并且在界面上使用 Out 和 In 时，绑定将不再起作用。

那么如何将其与 Ninject 绑定？

using System;
using Ninject;
using System.Collections.Generic;
using System.Linq;

namespace NinjectPlayGround
{
    class Program
    {
        static void Main(string[] args)
        {
            var kernel = new StandardKernel();

            //How to bind this?
            kernel.Bind(typeof(ICreateOrders<,>)).To<HorseOrderCreator>();
            //kernel.Bind<ICreateOrders<IOrderRequest, IOrderResponse>>().To(typeof(OrderCreator));

            kernel.Bind<IOrderCreatorFactory>().To<OrderCreatorFactory>();

            var factory = kernel.Get<IOrderCreatorFactory>();

            var orderCreator = factory.GetOrderCreator(new OrderRequest());
            var create = orderCreator.Create(new OrderRequest());

        }
    }
    public class OrderRequest : IOrderRequest
    {

    }
    public class OrderResponse : IOrderResponse
    {

    }
    public class HorseOrderRequest : IOrderRequest
    {

    }
    public class HorseOrderResponse : IOrderResponse
    {
        public string HorseName { get; set; }
    }
    public class HorseOrderCreator : ICreateOrders<HorseOrderRequest, HorseOrderResponse>
    {        
        public HorseOrderResponse Create(HorseOrderRequest orderRequest)
        {
            return new HorseOrderResponse() { HorseName = "Fred" };
        }
    }
    public class OrderCreator : ICreateOrders<OrderRequest, OrderResponse>
    {        

        public OrderResponse Create(OrderRequest orderRequest)
        {
            throw new NotImplementedException();
        }
    }
    public class OrderCreatorFactory : IOrderCreatorFactory
    {
        private readonly IEnumerable<ICreateOrders<IOrderRequest, IOrderResponse>> createOrders;
        public OrderCreatorFactory(IEnumerable<ICreateOrders<IOrderRequest, IOrderResponse>> createOrders)
        {
            this.createOrders = createOrders;
        }

        public ICreateOrders<IOrderRequest, IOrderResponse> GetOrderCreator(IOrderRequest orderRequest)
        {
            //Based on orderRequest i find the implementation i need.
        }
    }
    public interface ICreateOrders<TOrderRequest, TOrderResponse> where TOrderRequest : IOrderRequest where TOrderResponse : IOrderResponse
    {
        TOrderResponse Create(TOrderRequest orderRequest);
    }
    public interface IOrderCreatorFactory
    {
        ICreateOrders<IOrderRequest, IOrderResponse> GetOrderCreator(IOrderRequest orderRequest);
    }
    public interface IOrderRequest
    {

    }
    public interface IOrderResponse
    {

    }
}

Answer 1

因为 HorseOrderCreator 是一个 closed 泛型，将它绑定到 open 确实没有意义通用 typeof(ICreateOrders<,>)。毕竟，HorseOrderCreator 永远不会 成为 ICreateOrders<Foo, Bar>!

此外，无论使用何种 DI 容器，您当前的代码都无法正常工作。试试这个：

ICreateOrders<IOrderRequest, IOrderResponse> createOrders =
    (ICreateOrders<IOrderRequest, IOrderResponse>)new HorseOrderCreator();

结果：

System.InvalidCastException Unable to cast object of type 'HorseOrderCreator' to type 'ICreateOrders`2[NinjectPlayGround.IOrderRequest,NinjectPlayGround.IOrderResponse]'.

所以你的工厂将永远能够return一个HorseOrderCreator鉴于当前的接口限制。

所以这是一个设计问题。不是 DI 问题。并且该设计还可能包括界面的使用者，这些使用者未在问题中提供。所以我建议包括它们。

Answer 2

这就是我在你之前的问题中评论的重点 "The empty implementation of Create and the this.createOrders.First() somewhate obfuscates what you want to achieve"

总之，这可能符合您的需要。它主要依赖于ICreateOrders

中的CanHandle方法

using System;
using Ninject;
using System.Collections.Generic;
using System.Linq;

namespace NinjectPlayGround
{   
    class Program
    {
        static void Main(string[] args)
        {
            var kernel = new StandardKernel();

            //How to bind this?
            kernel.Bind<ICreateOrders<IOrderRequest, IOrderResponse>>().To(typeof(OrderCreator));
            kernel.Bind<ICreateOrders<IOrderRequest, IOrderResponse>>().To(typeof(HorseOrderCreator));

            kernel.Bind<IOrderCreatorFactory>().To<OrderCreatorFactory>();

            var factory = kernel.Get<IOrderCreatorFactory>();

            var orderCreator = factory.GetOrderCreator(new OrderRequest());
            var orderResponse = orderCreator.Create(new OrderRequest());    
            if (!(orderResponse is OrderResponse)) throw new InvalidCastException();

            var horseOrderCreator = factory.GetOrderCreator(new HorseOrderRequest());
            var horseResponse = horseOrderCreator.Create(new HorseOrderRequest());    
            if (!(horseResponse is HorseOrderResponse)) throw new InvalidCastException();

            Console.WriteLine("All resolutions successfull");
            Console.ReadLine();

        }
    }
    public class OrderRequest : IOrderRequest
    {

    }
    public class OrderResponse : IOrderResponse
    {

    }
    public class HorseOrderRequest : IOrderRequest
    {

    }
    public class HorseOrderResponse : IOrderResponse
    {
        public string HorseName { get; set; }
    }

    public abstract class BaseOrderCreator<TOrderRequest, TOrderResponse> : ICreateOrders<IOrderRequest, IOrderResponse> where TOrderRequest : IOrderRequest where TOrderResponse : IOrderResponse
    {
        public bool CanHandle(IOrderRequest request)
        {
            return request is TOrderRequest;
        }

        public abstract TOrderResponse SpecificCreate(TOrderRequest orderRequest);

        public IOrderResponse Create(IOrderRequest orderRequest)
        {
            return this.SpecificCreate((TOrderRequest)orderRequest);
        }
    }

    public class HorseOrderCreator : BaseOrderCreator<HorseOrderRequest, HorseOrderResponse>
    {
        public override HorseOrderResponse SpecificCreate(HorseOrderRequest orderRequest)
        {
            return new HorseOrderResponse() { HorseName = "Fred" };
        }
    }
    public class OrderCreator : BaseOrderCreator<OrderRequest, OrderResponse>
    {
        public override OrderResponse SpecificCreate(OrderRequest orderRequest)
        {
            return new OrderResponse();
        }
    }
    public class OrderCreatorFactory : IOrderCreatorFactory
    {
        private readonly IEnumerable<ICreateOrders<IOrderRequest, IOrderResponse>> createOrders;
        public OrderCreatorFactory(IEnumerable<ICreateOrders<IOrderRequest, IOrderResponse>> createOrders)
        {
            this.createOrders = createOrders;
        }

        public ICreateOrders<IOrderRequest, IOrderResponse> GetOrderCreator(IOrderRequest orderRequest)
        {
            return createOrders.FirstOrDefault(co => co.CanHandle(orderRequest));
        }
    }
    public interface ICreateOrders<in TOrderRequest, out TOrderResponse> where TOrderRequest : IOrderRequest where TOrderResponse : IOrderResponse
    {
        bool CanHandle(IOrderRequest request);

        TOrderResponse Create(TOrderRequest orderRequest);
    }
    public interface IOrderCreatorFactory
    {
        ICreateOrders<IOrderRequest, IOrderResponse> GetOrderCreator(IOrderRequest orderRequest);
    }
    public interface IOrderRequest
    {

    }
    public interface IOrderResponse
    {

    }
}

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