switch expressions in Dart

Dart 3's switch yields a value, with relational patterns and _.

void main() {
  const windKts = 18;
  // A switch expression yields a value; ranges match with relational
  // patterns and _ is the default.
  final flag = switch (windKts) {
    < 6 => 'calm: mist nets up',
    >= 6 && < 22 => 'workable breeze',
    _ => 'too rough for the ridge',
  };
  print('Wind $windKts kts: $flag');

  // The statement form still works for side effects per case.
  switch (flag.split(':').first) {
    case 'calm':
      print('Listen for warblers');
    default:
      print('Scan the open water');
  }
}

How it works

1. switch (windKts) as an expression assigns whichever arm matches.
2. < 6 and >= 6 && < 22 are relational patterns; _ is the default.
3. The statement form still exists for side effects per case.

Keywords and builtins used here

• case
• const
• default
• final
• switch
• void

The run, in numbers

Lines

19

Characters to type

482

Tokens

100

Three-star pace

65 tpm

At the three-star pace of 65 tokens a minute, this run takes about 92 seconds.

Type this snippet

Step 2 of 3 in Control flow, step 5 of 27 in Language basics.

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