c# - 消除工厂中的 IoC 容器耦合

Question

我有多个多语言“网站”在单个网络应用程序下运行。每个“语言环境”都有自己的 Solr 核心(在所有语言环境中具有相同的字段)。我正在使用 SolrNet 执行我的搜索查询。

为了根据每个请求切换内核，我正在注册一个 ISolrOperations<SearchResult> 的命名实例在我的每个语言环境的 Autofac 容器中(对于那些不熟悉 SolrNet 的人，这实际上是我进入库以进行查询的入口点)。

然后我有一个 ISearchService界面，带混凝土SolrSearchService实现，其构造函数签名如下所示:

public SolrSearchService(ISolrOperations<SearchResult> solr)

为了根据每个请求动态切换核心，我的 Controller 采用(注入(inject)的)ISearchServiceFactory而不是简单的 ISearchService .我的SolrSearchServiceFactory看起来像这样:

public class SolrSearchServiceFactory : ISearchServiceFactory
{
    private readonly IComponentContext _ctx;

    public SolrSearchServiceFactory(IComponentContext ctx)
    {
        _ctx = ctx;
    }

    public ISearchService Create(string id)
    {
        var result = _ctx.ResolveNamed<ISolrOperations<SearchResult>>(id);
        return new SolrSearchService(result);
    }
}

id只是语言环境标识符。这是我为将 Autofac 与我的服务/ Controller 分离但保持按请求切换内核的能力(基于 Controller 中执行的逻辑)所做的最好的事情。

然而，我对此仍然不是很满意，因为工厂本身仍然与 Autofac 耦合。有没有办法解决这个问题(从 SolrNet 或 Autofac 的角度来看)？

我看过使用 Autofac 的工厂代表，但似乎没有办法在这种情况下应用它们。

Answer 1

您可以使用键控/命名服务和 IIndex 来执行此操作，autofac 页面上有一个很好的条目 here .

这是一个简单的示例:

    public class Factory
    {
        private readonly IIndex<string, ISearchService> _index;

        public Factory(IIndex<string, ISearchService> index)
        {
            _index = index;
        }

        public ISearchService Resolve(string id)
        {
            return _index[id];
        }
    }

        // Registrations
        var builder = new ContainerBuilder();
        builder.Register<ASearchService>(c => new ASearchService()).Keyed<ISearchService>("A");
        builder.Register<BSearchService>(c => new BSearchService()).Keyed<ISearchService>("B");
        builder.Register<Factory>(c => new Factory(c.Resolve<IIndex<string, ISearchService>>()));
        // as per autofac's page linked above, autofac automatically implements IIndex types

        // Usage

        var aSearchService = fact.Resolve("A");

编辑:我认为我们可以做得更好，所以这里有几个扩展方法来避免创建显式工厂类:

    public delegate TReturn AutoFactoryDelegate<TParam, TReturn>(TParam param);

    public class AutoFactory<TParam, TReturn>
    {
        private readonly IIndex<TParam, TReturn> _index;

        public AutoFactory(IIndex<TParam, TReturn> index)
        {
            _index = index;
        }

        public TReturn Resolve(TParam param)
        {
            return _index[param];
        }
    }

    public delegate TReturn AutoFactoryDelegate<TParam, TReturn>(TParam param);

    public static class AutofacExtensions
    {
        public static void RegisterAutoFactoryDelegate<TParam, TReturn>(this ContainerBuilder builder)
        {
            builder.Register(c => new AutoFactory<TParam, TReturn>(c.Resolve<IIndex<TParam, TReturn>>()));

            builder.Register<AutoFactoryDelegate<TParam, TReturn>>(c =>
               {
                 var fact = c.Resolve<AutoFactory<TParam, TReturn>>();
                 return fact.Resolve;
               });
        }
    }

// Registration
var builder = new ContainerBuilder();
builder.Register<ASearchService>(c => new ASearchService()).Keyed<ISearchService>("A");
builder.Register<BSearchService>(c => new BSearchService()).Keyed<ISearchService>("B");
builder.RegisterAutoFactoryDelegate<string, ISearchService>();

// Usage
// fact is an AutoFactoryDelegate<string, ISearchService>
var aSearchService = fact("A");

编辑 2:再次查看后，我们不需要工厂类，因为 IIndex 实际上已经是工厂了。这导致实现方面的相当大的简化:

public static void RegisterAutoFactoryDelegate<TParam, TReturn>(this ContainerBuilder builder)
{
    builder.Register(c =>
                        {
                            var iindex = c.Resolve<IIndex<TParam, TReturn>>();
                            return (Func<TParam, TReturn>) (id => iindex[id]);
                        });
}

// Registration
var builder = new ContainerBuilder();
builder.Register<ASearchService>(c => new ASearchService()).Keyed<ISearchService>("A");
builder.Register<BSearchService>(c => new BSearchService()).Keyed<ISearchService>("B");
builder.RegisterAutoFactoryDelegate<string, ISearchService>();

// Usage
// fact is an Func<string, ISearchService>
var aSearchService = fact("A");