Records and structural patterns

The idea

Dart 3 records combine a fixed set of fields into an immutable aggregate. Positional fields are identified by position, while named fields are identified by name. A record type communicates the shape of a small result without requiring a new class. Record fields cannot be reassigned, although a referenced mutable object inside a field can still change.

Patterns can destructure a known record or test whether a value has an expected shape. Use a checked pattern when external or broadly typed data might not match. Named field order does not change a record’s named shape, but changing a field name does. Keep a class when behavior or a long-lived domain abstraction matters; records work well for focused multi-value results.

void main() {
  final point = (x: 3, y: 5);
  final (x: left, y: top) = point;
  print(left + top);
  print(point == (y: 5, x: 3));
}

8
true

Destructuring binds both fields, and named-field order does not change the record’s shape or values.