Extension methods for easier, faster more clear null and destroyed state checking for UnityEngine.Object

UnityObjectNullExtensions.cs

using System;
using System.Linq.Expressions;
using System.Reflection;
using System.Runtime.CompilerServices;

#pragma warning disable IDE0041 // Use 'is null' check

namespace UnityObjectNullExtensions
{
    public static class UnityObjectNullExtensionsSafe
    {
        private static Func<UnityEngine.Object, IntPtr> getNativeObjPtr;

        static UnityObjectNullExtensionsSafe()
        {
            Type unityObjectType = typeof(UnityEngine.Object);
            FieldInfo fInfo = unityObjectType.GetField("m_CachedPtr", BindingFlags.Instance | BindingFlags.NonPublic);
            ParameterExpression objParm = Expression.Parameter(unityObjectType, "obj");
            Type delegateType = typeof(Func<,>).MakeGenericType(unityObjectType, typeof(IntPtr));
            MemberExpression fieldExpr = Expression.Field(objParm, fInfo);
            LambdaExpression lambda = Expression.Lambda(delegateType, fieldExpr, objParm);
            getNativeObjPtr = (Func<UnityEngine.Object, IntPtr>)lambda.Compile();
        }

        /// <summary>
        /// True if this <paramref name="unityObject"/> instance is destroyed or not yet initialized.
        /// </summary>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static bool IsDestroyed(this UnityEngine.Object unityObject)
        {
            return getNativeObjPtr(unityObject) == IntPtr.Zero;
        }

        /// <summary>
        /// True if this <paramref name="unityObject"/> reference is <c>null</c>.
        /// </summary>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static bool IsNull(this UnityEngine.Object unityObject)
        {
            return ReferenceEquals(unityObject, null);
        }

        /// <summary>
        /// True if this <paramref name="unityObject"/> reference is <c>null</c> or if the instance is destroyed<br/>
        /// Equivalent as testing <c><paramref name="unityObject"/> == null</c> but several times faster.
        /// </summary>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static bool IsNullOrDestroyed(this UnityEngine.Object unityObject)
        {
            return ReferenceEquals(unityObject, null) || getNativeObjPtr(unityObject) == IntPtr.Zero;
        }

        /// <summary>
        /// Return <c>null</c> when this <paramref name="unityObject"/> reference is null or destroyed, otherwise return the <paramref name="unityObject"/> instance<br/>
        /// Allow using null conditional and null coalescing operators with UnityEngine.Object derivatives while conforming to the "a destroyed object is equal to null" Unity concept.<br/>
        /// Example :<br/>
        /// <c>float x = myUnityObject.DestroyedAsNull()?.myFloatField ?? 0f;</c><br/>
        /// will evaluate to <c>0f</c> when <c>myUnityObject</c> is destroyed, instead of returning the value still available on the managed instance.
        /// </summary>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static T DestroyedAsNull<T>(this T unityObject) where T : UnityEngine.Object
        {
            if (ReferenceEquals(unityObject, null) || getNativeObjPtr(unityObject) == IntPtr.Zero)
                return null;

            return unityObject;
        }
    }
}