so i was learning about SWITCH and CASE Statements in dart language, in the course he explains the code but he don't get an error while i get one.
the error i get : Warning: Operand of null-aware operation '??' has type 'String' which excludes null. String ``userName = name ?? "Guest User";
My Code is
void learnCondExpr() {
String name = 'Yamix';
String userName = name ?? "Guest User";
print(userName);
}
can i get some help please :)
Dart, by default, will assume any variable you've declared can never be null. You won't be able to assign null to a variable, and at runtime it will throw an error. It will also complain if you try to treat a non-nullable variable like it could be null, which is what you're doing with '??'.
You can use the ? after a variable's type to tell Dart that your variable will accept null values. ?? allows us to handle null values without writing extra lines of code
In short, x = y ?? z can be described as
If the left operand (y) is null, then assign the right operand (z) ie.
void example(String? myString) {
String? y = myString;
String z = 'spam';
var x = y ?? z;
print(x);
}
void main() {
example('hello!');
example(null);
}
// Output:
// hello!
// spam
Notice that I've added '?' after 'String' on the 2nd line, letting Dart know that 'y' could be null. This prevents me getting an error later in the code where I try to use a null-aware operator (??) to assign it to 'x'.
I hope this helped give you some background beyond just resolving your issue! :)