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Assets/NavMesh/Examples/Scripts/NavMeshPrefabInstance.cs

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+using UnityEngine;
+using System.Collections.Generic;
+using UnityEngine.AI;
+
+[ExecuteInEditMode]
+[DefaultExecutionOrder(-102)]
+public class NavMeshPrefabInstance : MonoBehaviour
+{
+    [SerializeField]
+    NavMeshData m_NavMesh;
+    public NavMeshData navMeshData
+    {
+        get { return m_NavMesh; }
+        set { m_NavMesh = value; }
+    }
+
+    [SerializeField]
+    bool m_FollowTransform;
+    public bool followTransform
+    {
+        get { return m_FollowTransform; }
+        set { SetFollowTransform(value); }
+    }
+
+    NavMeshDataInstance m_Instance;
+
+    // Position Tracking
+    static readonly List<NavMeshPrefabInstance> s_TrackedInstances = new List<NavMeshPrefabInstance>();
+    public static List<NavMeshPrefabInstance> trackedInstances {get {return s_TrackedInstances; }}
+    Vector3 m_Position;
+    Quaternion m_Rotation;
+
+    void OnEnable()
+    {
+        AddInstance();
+
+        if (m_Instance.valid && m_FollowTransform)
+            AddTracking();
+    }
+
+    void OnDisable()
+    {
+        m_Instance.Remove();
+        RemoveTracking();
+    }
+
+    public void UpdateInstance()
+    {
+        m_Instance.Remove();
+        AddInstance();
+    }
+
+    void AddInstance()
+    {
+#if UNITY_EDITOR
+        if (m_Instance.valid)
+        {
+            Debug.LogError("Instance is already added: " + this);
+            return;
+        }
+#endif
+        if (m_NavMesh)
+            m_Instance = NavMesh.AddNavMeshData(m_NavMesh, transform.position, transform.rotation);
+
+        m_Rotation = transform.rotation;
+        m_Position = transform.position;
+    }
+
+    void AddTracking()
+    {
+#if UNITY_EDITOR
+        // At runtime we don't want linear lookup
+        if (s_TrackedInstances.Contains(this))
+        {
+            Debug.LogError("Double registration of " + this);
+            return;
+        }
+#endif
+        if (s_TrackedInstances.Count == 0)
+            NavMesh.onPreUpdate += UpdateTrackedInstances;
+        s_TrackedInstances.Add(this);
+    }
+
+    void RemoveTracking()
+    {
+        s_TrackedInstances.Remove(this);
+        if (s_TrackedInstances.Count == 0)
+            NavMesh.onPreUpdate -= UpdateTrackedInstances;
+    }
+
+    void SetFollowTransform(bool value)
+    {
+        if (m_FollowTransform == value)
+            return;
+        m_FollowTransform = value;
+        if (value)
+            AddTracking();
+        else
+            RemoveTracking();
+    }
+
+    bool HasMoved()
+    {
+        return m_Position != transform.position || m_Rotation != transform.rotation;
+    }
+
+    static void UpdateTrackedInstances()
+    {
+        foreach (var instance in s_TrackedInstances)
+        {
+            if (instance.HasMoved())
+                instance.UpdateInstance();
+        }
+    }
+
+#if UNITY_EDITOR
+    void OnValidate()
+    {
+        // Only when the instance is valid (OnEnable is called) - we react to changes caused by serialization
+        if (!m_Instance.valid)
+            return;
+        // OnValidate can be called several times - avoid double registration
+        // We afford this linear lookup in the editor only
+        if (!m_FollowTransform)
+        {
+            RemoveTracking();
+        }
+        else if (!s_TrackedInstances.Contains(this))
+        {
+            AddTracking();
+        }
+    }
+#endif
+}