DryIoC 将参数传递给基于泛型类型参数的开放泛型服务的构造函数

Question

假设我有这个服务和两个策略：

public class SomeService<TEntity> : ISomeService<TEntity>
{
    public SomeService(ICurrentDbContext context, IStrategy<TEntity>? delete = null)
         : base(context, delete ?? new DefaultStrategy<TEntity>())
        {}
}

public class DefaultStrategy<TEntity> : IStrategy<TEntity> {}

public class CustomStrategy<TEntity> : IStrategy<TEntity> {}

我当前的服务注册如下：

container.Register(typeof(ISomeService<>), typeof(SomeService<>), Reuse.Transient);

我想在这里实现的是如果泛型类型参数 T 实现了某个接口，例如 IFoo.否则，将其保留为默认值为 null 的参数。

在这两种情况下，第一个参数都应该被自动解析为已注册的依赖项。

暂时不知道该怎么做，我应该使用拦截器吗？

Answer 1

你可以这样做（但你的问题并不清楚为什么你有两种策略DefaultStrategy<TEntity>和CustomStrategy<TEntity>）。

using System.Linq;
using NUnit.Framework;

namespace DryIoc.IssuesTests
{
    [TestFixture]
    public class SO_DryIoC_pass_param_to_constructor_of_open_generic_service_based_on_generic_type_parameter
    {
        [Test]
        public void Test()
        {
            var container = new Container();

            container.Register(typeof(ISomeService<>), typeof(SomeService<>), Reuse.Transient,
                made: Parameters.Of.Details((req, p) => 
                    p.ParameterType.GetGenericDefinitionOrNull() == typeof(IStrategy<>) && 
                    p.ParameterType.GetGenericParamsAndArgs().Any(x => x.IsAssignableTo<IFoo>())
                    ? null                              // the default injection behavior 
                    : ServiceDetails.Of(value: null))   // otherwise return the `null` value
                );

            container.Register<ICurrentDbContext, MyDbContext>();
            container.Register(typeof(IStrategy<>), typeof(DefaultStrategy<>));

            var s1 = container.Resolve<ISomeService<OtherEntity>>();
            Assert.IsNull(((SomeService<OtherEntity>)s1).Delete);

            var s2 = container.Resolve<ISomeService<FooEntity>>();
            Assert.IsNotNull(((SomeService<FooEntity>)s2).Delete);
        }

        public interface ISomeService<TEntity> {}
        public class SomeService<TEntity> : ISomeService<TEntity>
        {
            public readonly IStrategy<TEntity> Delete;
            public SomeService(ICurrentDbContext context, IStrategy<TEntity> delete = null) => Delete = delete;
        }

        public interface IFoo {}
        public class FooEntity : IFoo {}

        public class OtherEntity {}

        public interface IStrategy<TEntity> {}
        public class DefaultStrategy<TEntity> : IStrategy<TEntity> { }
        public class CustomStrategy<TEntity> : IStrategy<TEntity> { }

        public interface ICurrentDbContext {}
        public class MyDbContext : ICurrentDbContext {}
    }
}