Introduce HitObjectProperty<T>

osu.Game/Rulesets/Objects/HitObjectProperty.cs

@@ -0,0 +1,44 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+#nullable disable
+
+using JetBrains.Annotations;
+using osu.Framework.Bindables;
+
+namespace osu.Game.Rulesets.Objects
+{
+    /// <summary>
+    /// Represents a wrapper containing a lazily-initialised <see cref="Bindable{T}"/>, backed by a temporary field used for <see cref="Value"/> storage until initialisation.
+    /// </summary>
+    public struct HitObjectProperty<T>
+    {
+        [CanBeNull]
+        private Bindable<T> backingBindable;
+
+        /// <summary>
+        /// A temporary field to store the current value to, prior to <see cref="Bindable"/>'s initialisation.
+        /// </summary>
+        private T backingValue;
+
+        /// <summary>
+        /// The underlying <see cref="Bindable{T}"/>, only initialised on first access.
+        /// </summary>
+        public Bindable<T> Bindable => backingBindable ??= new Bindable<T> { Value = backingValue };
+
+        /// <summary>
+        /// The current value, derived from and delegated to <see cref="Bindable"/> if initialised, or a temporary field otherwise.
+        /// </summary>
+        public T Value
+        {
+            get => backingBindable != null ? backingBindable.Value : backingValue;
+            set
+            {
+                if (backingBindable != null)
+                    backingBindable.Value = value;
+                else
+                    backingValue = value;
+            }
+        }
+    }
+}