Data Types in Dart

Understanding data types is a fundamental step in learning any programming language. In Dart, data types define the kind of data a variable can hold, such as numbers, text, or logical values. Dart is a strongly typed language, but it also provides flexibility with type inference using var and dynamic typing using dynamic.

In this comprehensive guide, we’ll cover:

• Introduction to Dart data types
• Numeric types: int and double
• Text type: String
• Boolean type: bool
• Type inference with var
• Dynamic typing with dynamic
• Null safety and nullable types
• Type conversions
• Best practices for using Dart data types
• Real-world examples and use cases

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Introduction to Dart Data Types

A data type in Dart specifies the kind of data a variable can store. Dart variables are declared using a type, which helps the compiler detect errors and optimize performance.

int age = 25;
double price = 99.99;
String name = "John Doe";
bool isLoggedIn = true;

Key Points

• Dart is statically typed, meaning types are checked at compile time.
• Dart supports type inference, allowing you to omit the type in certain cases.
• Dart has null safety, preventing null reference errors by distinguishing nullable and non-nullable types.

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Numeric Types in Dart

Dart supports two primary numeric types: int and double.

1. int – Integer Numbers

• Represents whole numbers without decimals.
• Can be positive or negative.
• Examples:

int age = 30;
int year = 2025;
int temperature = -5;

Operations with int

int a = 10;
int b = 3;
print(a + b); // 13
print(a - b); // 7
print(a * b); // 30
print(a ~/ b); // 3 (integer division)
print(a % b); // 1 (modulo)

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2. double – Floating-Point Numbers

• Represents numbers with decimal points.
• Examples:

double price = 19.99;
double pi = 3.14159;
double temperature = -5.5;

Operations with double

double a = 5.5;
double b = 2.0;
print(a + b); // 7.5
print(a - b); // 3.5
print(a * b); // 11.0
print(a / b); // 2.75

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Text Type in Dart

1. String – Text

• Used to store textual data.
• Can use single quotes ', double quotes ", or triple quotes '''/""" for multi-line strings.

String name = "John";
String greeting = 'Hello, Dart!';
String multiLine = '''
This is
a multi-line
string.
''';

String Interpolation

int age = 25;
String message = "My age is $age";
print(message); // My age is 25

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Boolean Type in Dart

1. bool – True or False

• Represents logical values.
• Only two values: true or false.

bool isLoggedIn = true;
bool hasAccess = false;

Conditional Example

bool isRaining = true;
if (isRaining) {
  print("Take an umbrella!");
} else {
  print("Enjoy the sun!");
}

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Type Inference with var

Dart allows type inference, where the compiler infers the variable type from the assigned value.

var name = "Alice"; // inferred as String
var age = 30;       // inferred as int
var price = 99.99;  // inferred as double

Note: Once a type is inferred, it cannot change.

var age = 25;
age = "twenty-five"; // ❌ Error: type mismatch

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Dynamic Typing with dynamic

The dynamic keyword allows variables to change type at runtime.

dynamic data = "Hello";
print(data); // Hello
data = 100;
print(data); // 100

dynamic disables compile-time type checking, so use it cautiously.

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Null Safety and Nullable Types

Dart introduced null safety to avoid null reference errors.

int? age = null; // nullable int
String? name;    // can be null

• Non-nullable types (default) cannot be null:

int age = 25;
// age = null; ❌ Error

• Nullable types are declared with ?.

int? score = null;
score = 100; // valid

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Type Conversions

Dart allows conversion between compatible types.

Examples

String strNumber = "42";
int number = int.parse(strNumber);
double decimal = double.parse("3.14");

int num = 10;
String numStr = num.toString();

Always handle exceptions when parsing strings.

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Best Practices for Using Dart Data Types

1. Prefer non-nullable types for safety.
2. Use var for simplicity, but know the inferred type.
3. Use dynamic sparingly – it bypasses compile-time checks.
4. Use final or const for immutable data.
5. Leverage type conversions to avoid runtime errors.
6. Use descriptive variable names to clarify type and purpose.

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Real-World Examples

Example 1: Simple User Profile

String username = "Alice";
int age = 30;
double height = 5.6;
bool isPremium = true;

print("User: $username, Age: $age, Height: $height, Premium: $isPremium");

Example 2: Dynamic Data

dynamic data = 100;
print(data); // 100
data = "Hello Dart!";
print(data); // Hello Dart!

Example 3: Nullable Score

int? score;
if (score == null) {
  print("Score not available");
} else {
  print("Score: $score");
}