Svelto.ECS/Utilities/WeakActionStruct.cs

using System;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

//careful, you must handle the destruction of the GCHandles!

namespace BetterWeakEvents
{
    public struct WeakAction<T1, T2> : IEquatable<WeakAction<T1, T2>>
    {
        public WeakAction(Action<T1, T2> listener)
        {
            ObjectRef = GCHandle.Alloc(listener.Target, GCHandleType.Weak);
#if !NETFX_CORE
            Method = listener.Method;

            if (Method.DeclaringType.GetCustomAttributes(typeof(CompilerGeneratedAttribute), false).Length != 0)
                throw new ArgumentException("Cannot create weak event to anonymous method with closure.");
#else
            Method = listener.GetMethodInfo();
        
            if (CustomAttributeExtensions.IsDefined(Method, typeof(CompilerGeneratedAttribute), false) == false)
                throw new ArgumentException("Cannot create weak event to anonymous method with closure.");
#endif
        }

        public bool Invoke(T1 data1, T2 data2)
        {
            if (ObjectRef.IsAllocated && ObjectRef.Target != null)
            {
                Method.Invoke(ObjectRef.Target, new object[] { data1, data2 });
                return true;
            }

            Release();
            return false;
        }

        public bool Equals(WeakAction<T1, T2> other)
        {
            return (Method.Equals(other.Method));
        }

        public void Release()
        {
            ObjectRef.Free();
        }

        readonly GCHandle ObjectRef;
        readonly MethodInfo Method;
    }

    public struct WeakAction<T> : IEquatable<WeakAction<T>>
    {
        public WeakAction(Action<T> listener)
        {
            ObjectRef = GCHandle.Alloc(listener.Target, GCHandleType.Weak);
#if !NETFX_CORE
            Method = listener.Method;

            if (Method.DeclaringType.GetCustomAttributes(typeof(CompilerGeneratedAttribute), false).Length != 0)
                throw new ArgumentException("Cannot create weak event to anonymous method with closure.");
#else
            Method = listener.GetMethodInfo();
        
            if (CustomAttributeExtensions.IsDefined(Method, typeof(CompilerGeneratedAttribute), false) == false)
                throw new ArgumentException("Cannot create weak event to anonymous method with closure.");
#endif
        }

        public bool Invoke(T data)
        {
            if (ObjectRef.IsAllocated && ObjectRef.Target != null)
            {
                Method.Invoke(ObjectRef.Target, new object[] { data });
                return true;
            }

            Release();
            return false;
        }

        public bool Equals(WeakAction<T> other)
        {
            return (Method.Equals(other.Method));
        }

        public void Release()
        {
            ObjectRef.Free();
        }

        readonly GCHandle ObjectRef;
        readonly MethodInfo Method;
    }

    public struct WeakAction : IEquatable<WeakAction>
    {
        public WeakAction(Action listener)
        {
            ObjectRef = GCHandle.Alloc(listener.Target, GCHandleType.Weak);
#if !NETFX_CORE
            Method = listener.Method;

            if (Method.DeclaringType.GetCustomAttributes(typeof(CompilerGeneratedAttribute), false).Length != 0)
                throw new ArgumentException("Cannot create weak event to anonymous method with closure.");
#else
            Method = listener.GetMethodInfo();
        
            if (CustomAttributeExtensions.IsDefined(Method, typeof(CompilerGeneratedAttribute), false) == false)
                throw new ArgumentException("Cannot create weak event to anonymous method with closure.");
#endif
        }

        public bool Invoke()
        {
            if (ObjectRef.IsAllocated && ObjectRef.Target != null)
            {
                Method.Invoke(ObjectRef.Target, null);
                return true;
            }

            Release();
            return false;
        }

        public bool Equals(WeakAction other)
        {
            return (Method.Equals(other.Method));
        }

        public void Release()
        {
            ObjectRef.Free();
        }

        readonly GCHandle ObjectRef;
        readonly MethodInfo Method;
    }


}