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Src/Unity/Scripts/Extensions/ConstraintExtensions.cs

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+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+using UnityEngine.Animations;
+using UnityEngine.Assertions;
+
+namespace BITKit
+{
+	public static class ConstraintExtensions
+	{
+		public static ParentConstraint SetParentConstraint(this Transform target, Transform parentSource,
+			ParentConstraint constraint = null)
+		{
+			Assert.IsTrue(!constraint || target == constraint.transform);
+
+			if (!constraint)
+			{
+				if (!parentSource) return null;
+				constraint = target.gameObject.GetOrAddComponent<ParentConstraint>();
+			}
+
+			// 清空已有约束
+			constraint.constraintActive = false;
+			for (int i = constraint.sourceCount - 1; i >= 0; i--)
+			{
+				constraint.RemoveSource(i);
+			}
+
+			// 无约束
+			if (!parentSource) return constraint;
+
+			// 设置新约束
+			constraint.AddSource(new ConstraintSource
+			{
+				sourceTransform = parentSource,
+				weight = 1,
+			});
+
+			// 设置 Position offset
+			var positionOffset = parentSource.InverseTransformPoint(target.position);
+			constraint.SetTranslationOffset(0, positionOffset);
+
+			// 设置 Rotation offset
+			var localForward = parentSource.InverseTransformDirection(target.forward);
+			var localUpward = parentSource.InverseTransformDirection(target.up);
+			var rotationOffset = Quaternion.LookRotation(localForward, localUpward).eulerAngles;
+			constraint.SetRotationOffset(0, rotationOffset);
+
+			// 激活约束
+			constraint.constraintActive = true;
+
+			return constraint;
+		}
+	}
+
+}

Src/Unity/Scripts/Extensions/ConstraintExtensions.cs.meta

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Src/Unity/Scripts/Extensions/GameObjectExtensions.cs

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+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace BITKit
+{
+	public static class GameObjectExtensions
+	{
+		public static T GetOrAddComponent<T>(this GameObject gameObject) where T : Component
+		{
+			return gameObject.TryGetComponent<T>(out var t) ? t : gameObject.AddComponent<T>();
+		}
+		public static T RemoveComponent<T>(this GameObject gameObject) where T : Component
+		{
+			var t = gameObject.GetComponent<T>();
+			if (t is null) return null;
+			Object.Destroy(t);
+			return t;
+		}
+	}
+}

Src/Unity/Scripts/Extensions/GameObjectExtensions.cs.meta

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