Svelto.ECS/SetEGIDWithoutBoxing.cs

using System.Runtime.CompilerServices;

namespace Svelto.ECS.Internal
{
    delegate void SetEGIDWithoutBoxingActionCast<T>(ref T target, EGID egid) where T : struct, IEntityComponent;

    static class SetEGIDWithoutBoxing<T> where T : struct, IEntityComponent
    {
        public static readonly SetEGIDWithoutBoxingActionCast<T> SetIDWithoutBoxing = MakeSetter();

        public static void Warmup() { }

        static SetEGIDWithoutBoxingActionCast<T> MakeSetter()
        {
            if (ComponentBuilder<T>.HAS_EGID)
            {
#if !ENABLE_IL2CPP                
                var method = typeof(Trick).GetMethod(nameof(Trick.SetEGIDImpl)).MakeGenericMethod(typeof(T));
                return (SetEGIDWithoutBoxingActionCast<T>) System.Delegate.CreateDelegate(
                    typeof(SetEGIDWithoutBoxingActionCast<T>), method);
#else
             return (ref T target, EGID egid) =>
             {
                 var needEgid = (target as INeedEGID);
                 needEgid.ID = egid;
                 target      = (T) needEgid;
             };
#endif
            }

            return null;
        }
        
        static class Trick
        {
            public static void SetEGIDImpl<U>(ref U target, EGID egid) where U : struct, INeedEGID
            {
                target.ID = egid;
            }
        }
    }
}