using System;

namespace NewLife
{
    /// <summary>弱引用</summary>
    /// <typeparam name="T"></typeparam>
    public class WeakReference<T> : WeakReference
    {
        /// <summary>实例化</summary>
        public WeakReference() : base(null) { }

        /// <summary>实例化</summary>
        /// <param name="target">目标对象</param>
        public WeakReference(T target) : base(target) { }

        /// <summary>实例化</summary>
        /// <param name="target">目标对象</param>
        /// <param name="trackResurrection"></param>
        public WeakReference(T target, bool trackResurrection) : base(target, trackResurrection) { }

        /// <summary>目标引用对象</summary>
        public new T Target
        {
            get { return (T)base.Target; }
            set { base.Target = value; }
        }

        /// <summary>尝试获取目标值</summary>
        /// <param name="target">目标对象</param>
        /// <returns></returns>
        public Boolean TryGetTarget(out T target)
        {
            target = Target;
            return IsAlive;
        }

        /// <summary>类型转换</summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        public static implicit operator T(WeakReference<T> obj)
        {
            if (obj != null && obj.Target != null) return obj.Target;
            return default(T);
        }

        /// <summary>类型转换</summary>
        /// <param name="target">目标对象</param>
        /// <returns></returns>
        public static implicit operator WeakReference<T>(T target)
        {
            return new WeakReference<T>(target);
        }
    }
}