How not to print a null value received from sqflite database?-CodePudding

I'm new to Flutter and I'm making a "Recipes app" to learn. I have this problem now:
I'm working with Sqflite and I have a page where I show the ingredients from the recipe, the sql query is OK, but the problem is that I'm getting the null values and I don't know what to do to hide them. I've tried conditions, operators like (condition ? X : Y), substitutions, and nothing seems to work. PS: Some variables are in spanish 'cause I talk that language.

IngredientModel:

class IngredienteModel {
  IngredienteModel(
      {this.idIngrediente,
      this.idListaIngredientes,
      this.amount,
      this.unit,
      this.name});

  int? idIngrediente;
  int? idListaIngredientes;
  String? amount;
  String? unit;
  String? name;

  factory IngredienteModel.fromJson(Map<String, dynamic> json) =>
      IngredienteModel(
          idIngrediente: json["id_ingrediente"],
          idListaIngredientes: json["id_lista_ingredientes"],
          amount: json["amount"],
          unit: json["unit"],
          name: json["name"]);

  Map<String, dynamic> toJson() => {
        "id_ingrediente": idIngrediente,
        "id_lista_ingredientes": idListaIngredientes,
        "amount": amount,
        "unit": unit,
        "name": name,
      };
}

The widget where I return the ingredients to show:

List<Widget> ingredientesList(
    List<IngredienteModel>? ingredientes, BuildContext context) {
  final List<Widget> _listaIng = [];
  int _index = 1;
  ingredientes!.forEach((element) {
    final _widgetTemp = Row(
          children: [
            Text(_index.toString()   ": "),
            Text(element.amount.toString()   " "),
            _unitText(element),
            Text(element.name.toString()),
          ],
        );
    _listaIng.add(_widgetTemp);
    _index = _index   1;
  });

  return _listaIng;
}
 
Widget _unitText(IngredienteModel ingmod) {
  if (ingmod.unit?.isEmpty) {
    return Text(" ");
  } else {
    return Text(ingmod.unit   " de ");
  }
}

In that last method _unitText I've tried many stuff to do the magic, but:

-I can't use "ingmod.unit?.isEmpty" in the conditional because:

A nullable expression can't be used as a condition. Try checking that the value isn't 'null' before using it as a condition.

-Can't use either "ingmod.unit.length == 0" because: The property 'length' can't be unconditionally accessed because the receiver can be 'null'. Try making the access conditional (using '?.') or adding a null check to the target ('!').

-Then, to return the "Ingredient unit Text" asumming that isn't null, I can't use " " to add Strings: "The operator ' ' can't be unconditionally invoked because the receiver can be 'null'. Try adding a null check to the target ('!').

If I fix the errors to run the app, I get this (as you can see, null values are visible):
[1]: https://i.stack.imgur.com/vDI6F.png

Thanks if you reached so far, hope you can help me. Greetings and happy coding!

CodePudding user response：

Try in all the fields of your fromJson method to put

json [variable] ?? DEFAULT VALUE

This what it does is that if that variable is not in the json, it sets that value by default