Functions

 

String say(String from, String msg,
    [String device = 'carrier pigeon', String mood]) {
  var result = '$from says $msg';
  if (device != null) {
    result = '$result with a $device';
  }
  if (mood != null) {
    result = '$result (in a $mood mood)';
  }
  return result;
}
print(say('Bob', 'Howdy');//Bob says Howdy with a carrier pigeon
print(say('Bob', 'Howdy','IPHONE'));//Bob says Howdy with a IPHONE
print(say('Bob', 'Howdy','IPHONE','happy'));//Bob says Howdy with a IPHONE (in a happy mood)

Conditional expressions

String playerName(String name) => name ?? 'Guest';
print(playerName('Tom')); //Tom
print(playerName(null)); //Guest