Data Types in Dart

Overview of Data Types

Dart is a statically typed language — every value has a type. Dart's type system is sound, meaning it catches type errors at compile time. The core built-in types are:

Numbers

int age = 25;
int hexValue = 0xCAFE;      // hexadecimal
double pi = 3.14159;
double scientfic = 1.5e4;   // 15000.0
num score = 98;             // can be int or double

Strings

String single = 'Hello';
String double_ = "World";
String multi = '''
  This is a
  multi-line string
''';
String interpolated = 'Sum: $${3 + 4}';  // Sum: 7

Booleans

bool isLoggedIn = true;
bool hasError = false;
print(isLoggedIn && !hasError);  // true

Lists

List<int> numbers = [1, 2, 3, 4, 5];
List<String> fruits = ['apple', 'banana', 'cherry'];
print(fruits[0]);   // apple
print(fruits.length); // 3

Maps

Map<String, int> scores = {
  'Alice': 95,
  'Bob': 88,
  'Carol': 92,
};
print(scores['Alice']);  // 95

Null

In Dart with null safety, variables cannot be null by default. Add ? to allow null:

String? middleName = null;  // nullable
String lastName = 'Smith';   // non-nullable (cannot be null)

Full Example

void main() {
  int age = 20;
  double gpa = 3.85;
  String name = 'Maria';
  bool isGraduated = false;
  List<String> courses = ['Math', 'Physics', 'CS'];
  Map<String, dynamic> profile = {
    'name': name,
    'age': age,
    'gpa': gpa,
  };

  print('Student: $${profile['name']}, Age: $${profile['age']}');
  print('GPA: $gpa, Graduated: $isGraduated');
  print('Courses: $courses');
}

Student: Maria, Age: 20
GPA: 3.85, Graduated: false
Courses: [Math, Physics, CS]

🧠 Quiz

Summary

Dart has a rich set of built-in types including int, double, String, bool, List, Set, Map, and Null. Dart's sound null safety prevents null reference errors by default. Add ? to a type to allow null values.