Null-aware operators

Learn ??, ?. and ??= operators.

Dart, with null safety, offers special operators to handle null: ??, ?. and ??=.

?? returns the right side if the left is null: name ?? 'Guest' — if name is null, returns 'Guest'; otherwise the value of name.

?. accesses a member only if not null: user?.name — if user is null, returns null; otherwise calls name. ??= assigns only if null.

Exercise Default with ??

Declare String? name = null;. Print with print(name ?? 'Guest'). Since name is null you should see 'Guest'.

Show example solution

void main() {
  String? name = null;
  print(name ?? 'Guest');
}

?? returns an expression: name ?? 'Guest' gives a value but does not change name. name is still null.

??= does assignment: name ??= 'Guest'; — if name is null, it sets it to 'Guest'. So if you read name later, you see 'Guest'.

Summary: ?? gives a default when reading; ??= assigns a default when writing. You choose based on your need.

Default operator

String? name; print(name ____ 'Guest');

Show answer

String? name; print(name ?? 'Guest');