Summary - Variables

Combine var, final, const and null safety to write a profile program.

Summary - Variables

In this group you learned five ways to declare variables in Dart: var (type inference), final (runtime constant), const (compile-time constant), late (deferred init) and nullable types (?).

Combining them you can write a real profile program. We will practice with two small tasks.

In later lessons we will use these keywords for function parameters, class fields and collections too. The foundation is laid here.

Exercise Profile program

Inside void main() declare three variables: var name = 'Alex', final age = 25, const city = 'London'. Then print with print('$name $age $city').

Show example solution

void main() {
  var name = 'Alex';
  final age = 25;
  const city = 'London';
  print('$name $age $city');
}

Exercise Final profile

Inside void main() declare final name = 'Zoe' and const birthYear = 1995. Print with print('$name $birthYear').

Show example solution

void main() {
  final name = 'Zoe';
  const birthYear = 1995;
  print('$name $birthYear');
}

Test yourself

Which is a compile-time constant?
- var
- final
- const
- late
Show answer

const — const is set at compile time.

Nullable email

String? email = ____;

Show answer

String? email = null;

All variable concepts

var

Type inference
final

Immutable
const

Compile-time
String?

Nullable

Next lesson: Integer types

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