CreateLayerConstants.cs

using UnityEngine;
using UnityEditor;
using System.IO;
using System.Text;

public class CreateLayerConstants
{
    const string CLASS_NAME = "LayerConstants";
    const string FILE_PATH = "Assets/Scripts/Generated/";


    
    [MenuItem("Assets/Update Layer Constants")]
    public static void UpdateLayerConstants()
    {
        string[] values = new string[32];
        for (var i = 0; i < 32; i++)
        {
            var newValue = LayerMask.LayerToName(i);
            if (newValue != values[i])
            {
                values[i] = newValue;
            }
        }
        WriteLayerClass(values);
    }

    public static string GetFilename()
    {
        return string.Format("{0}.cs", CLASS_NAME);
    }

    public static string GetPath()
    {
        return Path.Combine(FILE_PATH, GetFilename());
    }

    public static void WriteLayerClass(string[] values)
    {
        Debug.Log("Writing layer values!");
        var path = GetPath();
        var dir = Path.GetDirectoryName(path);
        if (!Directory.Exists(dir))
        {
            Directory.CreateDirectory(dir);
        }
        var toWrite = GenerateClassText(values);
        File.WriteAllText(path, toWrite);

        AssetDatabase.Refresh();
    }

    public static string GenerateClassText(string[] values)
    {
        var sb = new StringBuilder();
        sb.AppendFormat("public class {0} {{\n", CLASS_NAME);
        for (var i = 0; i < values.Length; i++)
        {
            if (string.IsNullOrEmpty(values[i]))
            {
                continue;
            }
            var layer = values[i];
            var constName = layer.ToUpper().Replace(' ', '_');
            sb.AppendFormat("\tpublic const string {0} = \"{1}\";\n", constName, layer);
            sb.AppendFormat("\tpublic const int {0}_NUMBER = {1};\n", constName, i);
            sb.AppendLine();
        }
        sb.Append("}");

        return sb.ToString();
    }
}