What is dart record ?

Overview

Dart Records (introduced in Dart 3.0) are anonymous immutable composite types — they bundle multiple values together without defining a full class. Think of them as lightweight, named tuples.

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Basic Record Syntax

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// Positional record
(int, String) person = (28, 'Alice');
print(person.$1); // 28   ← First field
print(person.$2); // Alice ← Second field

// Named record (recommended)
({String name, int age}) user = (name: 'Alice', age: 28);
print(user.name); // Alice
print(user.age);  // 28

// Mixed
(int, {String name}) mixed = (1, name: 'Bob');
print(mixed.$1);     // 1
print(mixed.name);   // Bob

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Records as Return Types (Key Use Case)

Before records, you needed a class or List to return multiple values:

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// ❌ Old way — need a Map or class
Map<String, dynamic> fetchUser() {
  return {'user': user, 'token': token};
}

// ✅ Record — type-safe multiple return values
(User, String) fetchUserAndToken() {
  return (currentUser, authToken);
}

// Destructure on use
final (user, token) = fetchUserAndToken();
print(user.name); // Alice
print(token);     // Bearer xyz...

// Named record — more readable
({User user, String token}) login() {
  return (user: currentUser, token: authToken);
}
final result = login();
print(result.user.name);
print(result.token);

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Record Features

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// Records are equal if all fields are equal
final r1 = (1, 'Alice');
final r2 = (1, 'Alice');
print(r1 == r2); // true ✅ (unlike class instances)

// Records are immutable — no field mutation
({String name, int age}) rec = (name: 'Bob', age: 30);
// rec.name = 'Alice'; // ❌ Not allowed

// Pattern matching with records (Dart 3)
switch (rec) {
  case (name: final n, age: final a) when a > 18:
    print('Adult: $n');
}

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Typedef for Reusable Record Types

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typedef Coordinate = (double lat, double lng);

Coordinate getLocation() => (12.9716, 77.5946);

final (lat, lng) = getLocation();
print('$lat, $lng'); // 12.9716, 77.5946

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Records vs Classes vs Maps

Best Use Case: Return multiple typed values from a function without creating a full class. Use named records for clarity.