依赖注入 – 容器根据标准解决

发布时间：2020-12-14 04:54:50 所属栏目：百科来源：网络整理

导读：我正在尝试在使用Windsor容器时实现策略模式.这是我有的： public class OrderProcessor {... public OrderProcessor(ITaxStrategy strategy) {} public void Process(Order order) { order.Tax = strategy.CalcTax(order); }} 问题是,如何配置我的容器(其他

我正在尝试在使用Windsor容器时实现策略模式.这是我有的：

public class OrderProcessor {
...
    public OrderProcessor(ITaxStrategy strategy) {}

    public void Process(Order order)
    { 
      order.Tax = strategy.CalcTax(order);
    }
}

问题是,如何配置我的容器(其他容器示例欢迎),基本上具有选择适当依赖项的标准.所以,如果我注册以下内容

public class USTaxStrategy : ITaxStrategy { ... }
public class CanadaTaxStrateg : ITaxStrategy { ... }

如何使用Order.Destination(地址)作为注入依赖项的标准？

解决方法

这里有几个选项,选择你最喜欢的那个.我通常使用第一个,这是最简单的.

[TestFixture]
public class TaxStrategyTests {
    [Test]
    public void InjectWithFactory() {
        var container = new WindsorContainer();
        container.AddComponent<USTaxStrategy>();
        container.AddComponent<CanadaTaxStrategy>();
        container.AddComponent<OrderProcessor>();
        container.AddComponent<ITaxStrategyFactory,TaxStrategyFactory>();
        var order = new Order {Country = "US"};
        container.Resolve<OrderProcessor>().Process(order);
        Assert.AreEqual(10,order.Tax);
    }

    [Test]
    public void InjectWithFactoryFromDictionary() {
        var container = new WindsorContainer();
        container.AddFacility<FactorySupportFacility>();
        container.AddComponent<USTaxStrategy>();
        container.AddComponent<CanadaTaxStrategy>();
        container.AddComponent<OrderProcessor>();
        container.Register(Component.For<ITaxStrategyFactory>()
                               .UsingFactoryMethod(kernel => new TaxStrategyFactory2(new Dictionary<string,ITaxStrategy> {
                                   {"US",kernel.Resolve<USTaxStrategy>()},{"CA",kernel.Resolve<CanadaTaxStrategy>()},})));
        var order = new Order { Country = "US" };
        container.Resolve<OrderProcessor>().Process(order);
        Assert.AreEqual(10,order.Tax);
    }

    [Test]
    public void InjectWithProxy() {
        var container = new WindsorContainer();
        container.AddComponent<USTaxStrategy>();
        container.AddComponent<CanadaTaxStrategy>();
        container.AddComponent<OrderProcessorInterceptor>();
        container.AddComponent<ITaxStrategyFactory,TaxStrategyFactory>();
        container.Register(Component.For<OrderProcessor2>()
                               .LifeStyle.Transient
                               .Interceptors(InterceptorReference.ForType<OrderProcessorInterceptor>()).First);
        var order = new Order {Country = "CA"};
        container.Resolve<OrderProcessor2>().Process(order);
        Assert.AreEqual(5,order.Tax);
    }

    public class OrderProcessorInterceptor : IInterceptor {
        private readonly ITaxStrategyFactory strategyFactory;

        public OrderProcessorInterceptor(ITaxStrategyFactory strategyFactory) {
            this.strategyFactory = strategyFactory;
        }

        public void Intercept(IInvocation invocation) {
            if (invocation.MethodInvocationTarget.Name == "Process") {
                var processor = (OrderProcessor2) invocation.InvocationTarget;
                var order = (Order) invocation.Arguments[0];
                processor.Strategy = strategyFactory.Create(order);
            }
            invocation.Proceed();
        }
    }

    public interface IOrderProcessor {
        void Process(Order order);
    }

    public class OrderProcessor2 : IOrderProcessor {
        public ITaxStrategy Strategy { get; set; }

        public virtual void Process(Order order) {
            order.Tax = Strategy.CalcTax(order);
        }
    }

    public class OrderProcessor : IOrderProcessor {
        private readonly ITaxStrategyFactory strategyFactory;

        public OrderProcessor(ITaxStrategyFactory strategyFactory) {
            this.strategyFactory = strategyFactory;
        }

        public void Process(Order order) {
            var strategy = strategyFactory.Create(order);
            order.Tax = strategy.CalcTax(order);
        }
    }

    public interface ITaxStrategyFactory {
        ITaxStrategy Create(Order o);
    }

    public class TaxStrategyFactory : ITaxStrategyFactory {
        private readonly IKernel kernel;

        public TaxStrategyFactory(IKernel kernel) {
            this.kernel = kernel;
        }

        public ITaxStrategy Create(Order o) {
            if (o.Country == "US")
                return kernel.Resolve<USTaxStrategy>();
            return kernel.Resolve<CanadaTaxStrategy>();
        }
    }

    public class TaxStrategyFactory2: ITaxStrategyFactory {
        private readonly IDictionary<string,ITaxStrategy> strategies;

        public TaxStrategyFactory2(IDictionary<string,ITaxStrategy> strategies) {
            this.strategies = strategies;
        }

        public ITaxStrategy Create(Order o) {
            return strategies[o.Country];
        }
    }

    public interface ITaxStrategy {
        decimal CalcTax(Order order);
    }

    public class USTaxStrategy : ITaxStrategy {
        public decimal CalcTax(Order order) {
            return 10;
        }
    }

    public class CanadaTaxStrategy : ITaxStrategy {
        public decimal CalcTax(Order order) {
            return 5;
        }
    }

    public class Order {
        public string Country { get; set; }
        public decimal Tax { get; set; }
    }
}

（编辑：李大同）

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