Operators

An operator is a symbol that works on values, like + or &&.

Arithmetic and assignment

void main() {
  var score = 10;
  score += 5;
  score -= 2;
  score *= 2;
  score++;
  score ~/= 3;
  print(score);
}

9

Logical operators

void main() {
  final age = 20;
  final hasTicket = true;

  print(age >= 18 && hasTicket);
  print(age < 13 || age > 65);
  print(!hasTicket);
}

true
false
false

• && (and) — true only if both sides are true.
• || (or) — true if either side is true.
• ! (not) — flips true and false.

The conditional operator

condition ? valueIfTrue : valueIfFalse picks one of two values:

void main() {
  final temperature = 30;
  final advice = temperature > 25 ? 'Wear a hat' : 'Bring a jacket';
  print(advice);
}

Wear a hat

Type test operators

is checks a value's type; as casts it:

void main() {
  Object value = 'hello';
  print(value is String);
  print(value is int);
}

true
false

Cascade operator: ..

.. calls several methods on the same object, in sequence:

void main() {
  final buffer = StringBuffer()
    ..write('Dart')
    ..write(' ')
    ..write('rocks');
  print(buffer);
}

Dart rocks

Cascades are very common in Flutter and when configuring objects.

Practice

A shop gives free delivery if an order is over 50 or the customer is a member. With total = 42 and isMember = true, print Free delivery or Delivery: 5 EUR using the conditional operator.

void main() {
  const total = 42;
  const isMember = true;
  print(total > 50 || isMember ? 'Free delivery' : 'Delivery: 5 EUR');
}

Free delivery