main() {
// The ?? operator returns the first expression IFF it is not null
var monday = 'doctor';
var tuesday;
var next = tuesday ?? monday;
print('next appointment: $next');
// the ??= operator assigns a value IFF it is not null
var wednesday;
next ??= wednesday;
print('next appointment: $next');
// the ? operator calls a function IFF the object is not null
String thursday;
var length = thursday?.length;
print('length: $length');
}
$ dart nullaware.dart
next appoinment: doctor
next appointment: doctor
length: null