Dart Records
last modified June 7, 2025
In this article, we explore how to use records in the Dart programming language. Records provide a concise way to group multiple values into a single unit without requiring a custom class. They are immutable, ordered, and have a fixed size, making them an efficient alternative to traditional data structures.
Records in Dart function similarly to tuples in other programming languages. They allow developers to return multiple values from a function, store related data conveniently, and maintain clean, readable code. Unlike lists, which offer dynamic size and mutability, records are designed to be lightweight and predictable.
A key advantage of using records is improved type safety and structure. Each field in a record maintains its distinct type, ensuring that data remains properly categorized. This makes records particularly useful when working with temporary, grouped data in scenarios such as function outputs and intermediate calculations.
By leveraging records, Dart developers can write more expressive, concise, and efficient code without unnecessary boilerplate. In the following sections, we will demonstrate how to create and work with records effectively.
Dart Records Simple Example
The following example demonstrates how to create and use a simple record in Dart.
void main() {
// Creating a record
final person = ('John', 30, true);
// Accessing record elements
print('Name: ${person.$1}');
print('Age: ${person.$2}');
print('Is Active: ${person.$3}');
}
In this program, we create a record containing a name, age, and active status. We then access and print each element of the record.
final person = ('John', 30, true);
We create a record with three elements: a string, an integer, and a boolean.
print('Name: ${person.$1}');
print('Age: ${person.$2}');
print('Is Active: ${person.$3}');
We access the elements of the record using the $1, $2, and $3 syntax.
$ dart main.dart Name: John Age: 30 Is Active: true
Dart Records with Named Fields
Records can also have named fields, which make the code more readable and self-explanatory.
void main() {
// Creating a record with named fields
final person = (name: 'Alice', age: 25, isActive: false);
// Accessing record elements using named fields
print('Name: ${person.name}');
print('Age: ${person.age}');
print('Is Active: ${person.isActive}');
}
In this program, we create a record with named fields and access the elements using the field names.
final person = (name: 'Alice', age: 25, isActive: false);
We create a record with named fields: name, age, and
isActive.
print('Name: ${person.name}');
print('Age: ${person.age}');
print('Is Active: ${person.isActive}');
We access the elements of the record using the named fields.
$ dart main.dart Name: Alice Age: 25 Is Active: false
Dart Records in Functions
Records are particularly useful for returning multiple values from a function.
(String, int) getUserInfo() {
return ('Bob', 40);
}
void main() {
final userInfo = getUserInfo();
print('Name: ${userInfo.$1}');
print('Age: ${userInfo.$2}');
}
In this program, we define a function that returns a record containing a name and age. We then call the function and access the returned values.
(String, int) getUserInfo() {
return ('Bob', 40);
}
We define a function that returns a record with two elements: a string and an integer.
final userInfo = getUserInfo();
print('Name: ${userInfo.$1}');
print('Age: ${userInfo.$2}');
We call the function and access the returned record's elements.
$ dart main.dart Name: Bob Age: 40
Dart Records with Pattern Matching
Dart supports pattern matching, which allows you to destructure records into individual variables.
void main() {
final person = ('Charlie', 35, true);
// Destructuring the record
final (name, age, isActive) = person;
print('Name: $name');
print('Age: $age');
print('Is Active: $isActive');
}
In this program, we use pattern matching to destructure a record into individual variables.
final (name, age, isActive) = person;
We destructure the record into three variables: name,
age, and isActive.
print('Name: $name');
print('Age: $age');
print('Is Active: $isActive');
We print the values of the destructured variables.
$ dart main.dart Name: Charlie Age: 35 Is Active: true
Dart Records as Map Keys
Records can be used as keys in Dart maps. Records with the same values are considered equal and have the same hash code.
void main() {
final record1 = ('apple', 1);
final record2 = ('banana', 2);
final record3 = ('apple', 1);
final map = {
record1: 'Red fruit',
record2: 'Yellow fruit',
};
print(map[record1]); // Red fruit
print(map[record3]); // Red fruit (record1 == record3)
}
In this example, record1 and record3 are equal, so
they refer to the same map entry.
Dart Records in Collections
You can store records in lists and sets. Dart uses value equality for records, so duplicates are not added to sets.
void main() {
final r1 = ('x', 10);
final r2 = ('y', 20);
final r3 = ('x', 10);
final list = [r1, r2, r3];
print(list);
final set = {r1, r2, r3};
print(set);
}
The set contains only two unique records, even though three were added.
Dart Records with Positional and Named Fields
A record can have both positional and named fields. You can access them using their respective syntax.
void main() {
final data = ('A', 42, flag: true, description: 'sample');
print('First: \'${data.$1}\'');
print('Second: ${data.$2}');
print('Flag: ${data.flag}');
print('Description: ${data.description}');
}
This record has two positional fields and two named fields. Access positional
fields with $1, $2 and named fields with their names.
Source
Dart Records - Language Documentation
In this article, we have covered the basics of using records in Dart. Records are a powerful feature for grouping data in a lightweight and immutable way.
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