Snippet 6: Promotion

main.dart

// With null safety, Dart takes null checks
// into account. Nullable variables that
// can't possibly contain null are treated
// like non-nullable variables.
// 
// This behavior is called "promotion."
//
// In the example below, add an if-then to
// the beginning of `getLength` that
// returns zero if `str` is null.

int getLength(String? str) {
  // Add null check here
  
  return str.length;  
}

void main() {
  print(getLength('This is a string!'));
}

Hello maybe This code should like this

int? getLength(String? str) {
  // Add null check here
  
  return str?.length;  
}

void main() {
  print(getLength('This is a string!'));
}

Thanks.