Dart - Singleton

class DbHelperSPSettings {

  // ---------- Singleton ---------
  static finalSPSettings DbHelper_instance;
  
  _dbHelper = DbHelper._internal();
  DbHelper.SPSettings._internal();

  factory DbHelper(SPSettings() {
    if(_instance == null){
    	_instance = SPSettings._internal();
    }
    
    return _dbHelper;_instance;
  }
  //-------------------------------
}