How do I get objects using layer name?

Question

I am creating an FPS game in local multiplayer. One player creates the hot-spot game, and the other one connects through WiFi network and plays the game.

I want to find all of the player objects on the network that have a specific layer name, and store them into an array when the player spawns on the network. I've been able to add the object to the array, but I can't find the layer's objects with what I found with Google searches.

LayerMask.NameToLayer("LayerName");

LayerMask.LayerToName(8);

This returns the name of layer and layer index. How can I get the objects using a specific layer name, and also store it in to an array?

Answer 1

It seems there is not any built-in function to do what you want, but you can write your own function to find every object in a given layer. However, be careful, the function is quite slow, so do not use it frequently :

GameObject[] FindGameObjectsInLayer(int layer)
{
    var goArray = FindObjectsOfType(typeof(GameObject)) as GameObject[];
    var goList = new System.Collections.Generic.List<GameObject>();
    for (int i = 0; i < goArray.Length; i++)
    {
        if (goArray[i].layer == layer)
        {
            goList.Add(goArray[i]);
        }
    }
    if (goList.Count == 0)
    {
        return null;
    }
    return goList.ToArray();
}

Source : http://answers.unity3d.com/questions/179310/how-to-find-all-objects-in-specific-layer.html

---

If you have to frequently update the list, I advise you to update a Dictionary when a player connects / disconnect / changes layer. The following class can't be attached to a gameobject, simply instantiate it inside your players manager. I haven't tested the following code :

using UnityEngine ;
using System.Collections.Generic ;

private class PlayersManagerByLayer
{    
    private Dictionary<int,List<GameObject>> gameObjectsByLayer ;

    public PlayersManagerByLayer()
    {
        gameObjectsByLayer = new Dictionary<int,List<GameObject>>();
    }

    public void AddPlayer( GameObject player )
    {
        if( !gameObjectsByLayer.ContainsKey( player.layer ) )
            gameObjectsByLayer.Add( player.layer, new List<GameObject>() );

        if( !gameObjectsByLayer[player.layer].Contains(player ) )
            gameObjectsByLayer[player.layer].Add( player ) ;
    } 

    public void RemovePlayer( GameObject player )
    {
        if( gameObjectsByLayer.ContainsKey( player.layer ) && gameObjectsByLayer[player.layer].Contains(player ) )
            gameObjectsByLayer[player.layer].Remove( player ) ;
    }

    public void MovePlayerToLayer( GameObject player, int newLayer )
    {
        RemovePlayer( player ) ;
        player.layer = newLayer ;
        AddPlayer( player ) ;
    }

    public List<GameObject> GetPlayersFromLayer( int layer )
    {
        if( !gameObjectsByLayer.ContainsKey( layer ) )
            return null ;
        else
            return gameObjectsByLayer[layer] ;
    }

}