What is this unary postfix in dart/flutter?

Question

i saw this unary postfix in Dart/flutter code: ?.

like this:

videoController?.dispose();

and i want to know how it work...

Answer 1

This is a great feature in Dart

meaning is if and only if that object is not null otherwise, return null.

Simple example:

void main() {
  Person p1 = new Person("Joe");
  print(p1?.getName); // Joe

  Person p2;
  print(p2?.getName); // null

  //print(p2.getName); // this will give you an error because you cannot invoke a method or getter from a null
}

class Person {
  Person(this.name);
  String name;

  String get getName => name;
}

There are other cool null aware operators like ??. Read my QnA to find out more about null-aware operators.