How I can initialize _instance?

I get "Field ‘_instance’ has not been initialized"
Or any other ways to get rid of nullSafety,,,

here is the code:

   class ShoppingBasketData{ 
  static late ShoppingBasketData _instance ;
  
   late List<product> _basketItem;


  ShoppingBasketData(){
    _basketItem =<product>[];
  }

  List<product> get basketItem => _basketItem;

  set basketItem(List<product> value) {
    _basketItem = value;
  }

  static  ShoppingBasketData getInstance(){
    if (_instance == null){
      _instance  = ShoppingBasketData();
      
    }
    return _instance;
    }
 
}

>Solution :

What is wrong is that you declared _instance to be late. What that means is that you as a developer promise to initialize it before you access it. If you break that promise, you get an exception.

It seems that you want null to be a valid value, so what you need to do is make it nullable:

static ShoppingBasketData? _instance

You may also want to look into How do you build a Singleton in Dart? so you don’t have to reinvent the wheel, and you may want to look into Flutter state management, because singleton is probably the worst of all options.