3、手寫Unity容器--第N層依賴注入

這個場景跟《手寫Unity容器--第一層依賴注入》又不同，這里構造AndroidPhone的時候，AndroidPhone依賴于1個IPad，且依賴于1個IHeadPhone，而HeadPhone又依賴于1個IRootPhone

1、IPhone介面

namespace SimplestUnity_nLayer
{
    interface IPhone
    {
        void Call();
    }
}

2、AndroidPhone實作

namespace SimplestUnity_nLayer
{
    public class AndroidPhone : IPhone
    {
        public AndroidPhone(IPad iPad, IHeadPhone iHeadPhone)
        {
            Console.WriteLine("{0}建構式", this.GetType().Name);
        }
    }
}

3、IPad介面

namespace SimplestUnity_nLayer
{
    public interface IPad
    {
        void Show();
    }
}

4、IPad實作

namespace SimplestUnity_nLayer
{
    public class AndroidPad:IPad
    {
        public AndroidPad()
        {
            Console.WriteLine("{0}建構式", this.GetType().Name);
        }

        public void Show()
        {
            Console.WriteLine("看{0}", this.GetType().Name);
        }
    }
}

5、IHeadPhone介面

namespace SimplestUnity_nLayer
{
    public interface IHeadPhone
    {
        
    }
}

6、IHeadPhone實作

namespace SimplestUnity_nLayer
{
    public class HeadPhone : IHeadPhone
    {
        public HeadPhone(IRootPhone iRootPhone)
        {
            Console.WriteLine("Headphone 被構造");
        }
    }
}

7、IRootPhone介面

namespace SimplestUnity_nLayer
{
    public interface IRootPhone
    {
        
    }
}

8、IRootPhone實作

namespace SimplestUnity_nLayer
{
    public class RootPhone : IRootPhone
    {
        public RootPhone()
        {
            Console.WriteLine("RootPhone 被構造");
        }
    }
}

9、容器--介面

public interface IDavidContainer
{
    void RegisterType<TFrom, TTo>();
    
    T Resolve<T>();
}

10、容器--實作

namespace SimplestUnity_nLayer
{
    /// <summary>
    /// 容器--工廠
    /// </summary>
    public class DaivdContainer:IDaivdContainer
    {
        private Dictionary<string, Type> containerDictionary = new Dictionary<string, Type>();//字典

        /// <summary>
        /// 注冊型別
        /// </summary>
        /// <typeparam name="TFrom"></typeparam>
        /// <typeparam name="TTo"></typeparam>
        public void RegisterType<TFrom, TTo>()
        {
            containerDictionary.Add(typeof(TFrom).FullName, typeof(TTo));
        }

        /// <summary>
        /// 獲取實體
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public T Resolve<T>()
        {
            Type type = containerDictionary[typeof(T).FullName];
            return (T)this.CreateInstance(type);
        }

        private object CreateInstance(Type type)
        {
            //1、得到型別的所有建構式
            ConstructorInfo[] ctorArray = type.GetConstructors();

            //2、只得到有標記DavidInjectionConstructor特性的建構式，如果都沒有標記特性，那么得到引數最多的建構式
            ConstructorInfo currentCtor = null;

            if (ctorArray.Count(c => c.IsDefined(typeof(DavidInjectionConstructor), true)) > 0)
            {
                currentCtor = ctorArray.FirstOrDefault(c => c.IsDefined(typeof(DavidInjectionConstructor), true));//得到第1個標記DavidInjectionConstructor特性的建構式
            }
            else
            {
                currentCtor = ctorArray.OrderByDescending(c => c.GetParameters().Length).FirstOrDefault();//得到引數個數最多的建構式
            }
            List<object> paraList = new List<object>();
            //遞回：隱形的跳出條件，條件就是GetParameters結果為空，targetType擁有無引數建構式
            foreach (var para in currentCtor.GetParameters())
            {
                //得到的引數型別是IPad，抽象無法創建實體
                var paraType = para.ParameterType;
                //所以根據IPad Key，得到AndroidPad型別，具體型別就可以創建實體
                var targetParaType = containerDictionary[paraType.FullName];
                //繼續檢查targetParaType的建構式，不能直接創建實體了
                Object obj = this.CreateInstance(targetParaType);
                
                paraList.Add(obj);
            }
            return Activator.CreateInstance(type, paraList.ToArray());
        }
    }
}

11、呼叫

class Program
{
    static void Main(string[] args)
    {
        DaivdContainer davidContainer = new DaivdContainer();
        davidContainer.RegisterType<IPhone, AndroidPhone>();
        davidContainer.RegisterType<IPad, AndroidPad>();
        davidContainer.RegisterType<IHeadPhone, HeadPhone>();
        davidContainer.RegisterType<IRootPhone, RootPhone>();
        IPhone iphone = davidContainer.Resolve<IPhone>();
        iphone.Call();
    }
}

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