CODEWITHSUNDEEP
flutterdart
Manraj Singh
Manraj Singh

Reputation: 110

Cannot return Null from a non-nullable type function

This is the error message I am getting:

The body might complete normally, causing 'null' to be returned, but the return type is a potentially non-nullable type.
Try adding either a return or a throw statement at the end.

on the following code:

Product findProductById(String prodId) {
  _productsList.firstWhere((element) {
    return prodId == element.id;
  });
}

I want to find the Product by its id but if its not found what should I return?

Upvotes: 0

Views: 781

Answers (3)

sajalsd
sajalsd

Reputation: 399

You can return a empty Product it's not found.

  Product findProductById(String productId) {
    return productList.firstWhere((element) => element.id == productId,
        orElse: () => Product() // make a empty product using default constructor);
  }

Upvotes: 1

Tolga Kartal
Tolga Kartal

Reputation: 633

From Dart 2.12 and up, we need to specify whether if a type is nullable or non-nullable. In your case, you should add '?' question mark after the type name Product as you can see below, which will tell the compiler that your function can return a nullable product. Also you forgot to return the filtered product from the productList.

Product? findProductById(String prodId) {
return _productsList.firstWhere((element) {
  return prodId == element.id;
});

Upvotes: 1

enzo
enzo

Reputation: 11486

You're not returning inside the findProductById function:

Product findProductById(String prodId) {
  return _productsList.firstWhere((element) {
    return prodId == element.id;
  });
}

Upvotes: 1

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