NavWorld.GetHashCode

Returns

int The hash code derived from the internal identifier of this NavWorld, suitable for use in hash-based collections.

Description

Calculates the hash code for use in collections.

The returned value is derived from the internal identifier of the NavWorld and is suitable for storing worlds in hash-based collections such as Dictionary or HashSet. Two NavWorld values that compare equal through NavWorld.Equals also produce the same hash code.

The reverse doesn't hold. Two NavWorld handles that refer to different navigation data can produce the same hash code, so a matching hash code on its own doesn't establish that two handles are the same. Use NavWorld.Equals or the == operator whenever you need to determine that.

using UnityEngine;
using UnityEngine.AI;
using Unity.AI.Navigation.LowLevel;

public class NavWorldEqualityExample : MonoBehaviour
{
    NavWorld m_World;
    int m_CachedWorldHash;

    void OnEnable()
    {
        m_World = NavWorld.GetDefaultWorld();
        m_CachedWorldHash = m_World.GetHashCode();
        Debug.Log($"Cached the NavMesh world hash {m_CachedWorldHash}");
        CompareNavigationWorldToPrevious();

        // Destroying all the data makes every existing handle to the old world invalid.
        NavMesh.RemoveAllNavMeshData();
        Debug.Log($"Removed all NavMesh data.");

        //m_CachedWorldHash = m_World.GetHashCode();
        //Debug.Log($"Cached the NavMesh world, hash {m_CachedWorldHash}");
        CompareNavigationWorldToPrevious();
    }

    public void CompareNavigationWorldToPrevious()
    {
        NavWorld currentWorld = NavWorld.GetDefaultWorld();

        // Equals, == and != compare the underlying navigation system rather than the struct
        // copy, so two handles obtained from the same world always compare equal.
        if (currentWorld == m_World)
        {
            Debug.Log($"The navigation world is the same as before.");

            // The handles are interchangeable, so keep one and release the duplicate.
            currentWorld.Dispose();
            return;
        }

        Debug.Log($"The world was re-created: hash {m_CachedWorldHash} became {currentWorld.GetHashCode()}");

        // Release the stale handle before replacing it, otherwise its safety handle leaks.
        m_World.Dispose();
        m_World = currentWorld;
        m_CachedWorldHash = m_World.GetHashCode();
    }

    void OnDisable()
    {
        m_World.Dispose();
    }
}