I created a function to fetch data through api and now I'm trying to check from the data value of this function, but every time I get the following error:

The body might complete normally, causing 'null' to be returned, but the return type, 'FutureOr<List<AllProductModel>>', is a potentially non-nullable type.

my function:

Future <List<AllProductModel>> fetchYourProduct(Uid) async {
  final url =
      'https://*****************.php?UserPost='   Uid.toString();
  final response = await http.get(Uri.parse(url));
  final body = json.decode(response.body);
  if (json.decode(response.body)!="Data not found") { //here problem 
    return body.map<AllProductModel>(AllProductModel.fromJson).toList();
  }else{

  }
}

I try to make if statement to see if the data I get from api same string I was add or not. The function without if statement it's working fine but I need to add if statement.

Data model:

class AllProductModel {

  String? name;
 

  AllProductModel(
      {
        this.name,
      
 });

  static AllProductModel  fromJson(json) => AllProductModel(
 
    name : json['name'].toString(),

  );
  }

How I can solve this problem?

Thank you.

CodePudding user response：

With a function that has a non-nullable return type (return can't be null), you need to return that type in every possible case inside that function (or throw an exception).

For example, your function returns a Future<List<AllProductModel>>. This is not nullable, hence, for every single case of your function, you must either:

1. Return that specified type; or
2. Do a throw statement, like this: throw <some_exception>

You return something inside the if clause of your statement, however, you don't return anything inside the else clause. That's your problem.

Solution: Either return something inside that else clause, or throw an exception.

CodePudding user response：

You can also try and check if this works..

You can make the fetchYourProduct() function nullable by changing the return type from Future <List> to Future <List>?.

CodePudding user response：

Future <List> fetchYourProduct(Uid) async { final url = 'https://*****************.php?UserPost=' Uid.toString(); final response = await http.get(Uri.parse(url)); final body = json.decode(response.body); if (json.decode(response.body)!="Data not found") { //here problem return body.map(AllProductModel.fromJson).toList(); }else{ return []; } }

you should to return If and else both of statement compulsory.