Step 1 - Named parameters

void createUser({required String name, required int age}) {
  print('User: $name ($age)');
}

void main() {
  createUser(name: 'Rafi', age: 20);
}

• Named parameters use braces {}.
• required means caller must pass that value.

Step 2 - Optional named parameter with default value

void printGreeting(String name, {String title = 'Mr/Ms'}) {
  print('Hello $title $name');
}

void main() {
  printGreeting('Asha');
  printGreeting('Asha', title: 'Dr.');
}

• Default value is used when caller does not pass it.

Step 3 - Optional positional parameter (basic)

String formatName(String first, [String? last]) {
  if (last == null) {
    return first;
  }
  return '$first $last';
}

void main() {
  print(formatName('Shafi'));
  print(formatName('Shafiul', 'Islam'));
}

• Optional positional parameters use [].

Quick rule

• Use named parameters for clarity.
• Use positional parameters for short, obvious inputs.

Practice tasks

• Make a register function with required named params: email, password.
• Add an optional named param isAdmin = false.
• Make a function with one optional positional parameter.