3、手写Unity容器--第N层依赖注入

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

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

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

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

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

namespace SimplestUnity_nLayer
{
    public interface IHeadPhone
    {
        
    }
}

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

namespace SimplestUnity_nLayer
{
    public interface IRootPhone
    {
        
    }
}

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

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

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

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

        /// <summary>
        /// 获取实例
        /// </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、得到类型的所有构造函数
            ConstructorInfo[] ctorArray = type.GetConstructors();

            //2、只得到有标记DavidInjectionConstructor特性的构造函数，如果都没有标记特性，那么得到参数最多的构造函数
            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个标记DavidInjectionConstructor特性的构造函数
            }
            else
            {
                currentCtor = ctorArray.OrderByDescending(c => c.GetParameters().Length).FirstOrDefault();//得到参数个数最多的构造函数
            }
            List<object> paraList = new List<object>();
            //递归：隐形的跳出条件，条件就是GetParameters结果为空，targetType拥有无参数构造函数
            foreach (var para in currentCtor.GetParameters())
            {
                //得到的参数类型是IPad，抽象无法创建实例
                var paraType = para.ParameterType;
                //所以根据IPad Key，得到AndroidPad类型，具体类型就可以创建实例
                var targetParaType = containerDictionary[paraType.FullName];
                //继续检查targetParaType的构造函数，不能直接创建实例了
                Object obj = this.CreateInstance(targetParaType);
                
                paraList.Add(obj);
            }
            return Activator.CreateInstance(type, paraList.ToArray());
        }
    }
}

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();
    }
}