二、手寫Unity容器--第一層依賴注入

這個場景跟《手寫Unity容器--極致簡陋版Unity容器》不一樣，這裏構造AndroidPhone的時候，AndroidPhone依賴於1個IPad

一、IPhone接口

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

二、AndroidPhone實現

namespace SimplestUnity_OneLayer
{
    public class AndroidPhone : IPhone
    {
        public AndroidPhone()
        {
            Console.WriteLine("{0}構造函數", this.GetType().Name);
        }
    }
}

三、IPad接口

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

四、IPad實現

namespace SimplestUnity_OneLayer
{
    public class AndroidPad:IPad
    {
        public AndroidPad()
        {
            Console.WriteLine("{0}構造函數", this.GetType().Name);
        }

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

五、容器--接口

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

六、容器--實現

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

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

        /// <summary>
        /// 獲取實例
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public T Resolve<T>()
        {
            Type type = containerDictionary[typeof(T).FullName];
            //一、獲得類型的全部構造函數
            ConstructorInfo[] ctorArray = type.GetConstructors();

            //二、只獲得有標記DavidInjectionConstructor特性的構造函數，若是都沒有標記特性，那麼獲得參數最多的構造函數
            ConstructorInfo currentCtor = null;

            if (ctorArray.Count(c => c.IsDefined(typeof(DavidInjectionConstructor), true)) > 0)
            {
                currentCtor = ctorArray.FirstOrDefault(c => c.IsDefined(typeof(DavidInjectionConstructor), true));//獲得第1個標記DavidInjectionConstructor特性的構造函數
            }
            else
            {
                currentCtor = ctorArray.OrderByDescending(c => c.GetParameters().Length).FirstOrDefault();//獲得參數個數最多的構造函數
            }
            List<object> paraList = new List<object>();
            
            foreach (var para in currentCtor.GetParameters())
            {
                //獲得的參數類型是IPad，抽象沒法建立實例
                var paraType = para.ParameterType;
                //因此根據IPad Key，獲得AndroidPad類型，具體類型就能夠建立實例
                var targetParaType = containerDictionary[paraType.FullName];
                paraList.Add(Activator.CreateInstance(targetParaType));
            }
            return (T)Activator.CreateInstance(type,paraList.ToArray());
        }
    }
}

七、調用

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