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Dart – 2 – Variables and Data Types

In Dart, variables and data types serve as the building blocks of any program. They allow developers to store and manipulate information, ranging from simple integers to complex data structures. Understanding how to declare variables and work with different data types is fundamental to writing effective Dart code.

Declaring Variables

Before diving into data types, it’s crucial to grasp how to declare variables in Dart. Dart uses a straightforward syntax:

// Declaring variables
var name = 'John'; // Using var to declare a variable
int age = 30; // Explicitly specifying data type

In the example above, two variables, name and age, are declared. The first, name, uses the var keyword, allowing Dart to infer its data type. The second, age, explicitly specifies the int data type.

Data Types in Dart

Dart offers several data types to accommodate various kinds of information. These data types can be categorized into the following:

1. Numbers

Dart supports several numeric data types, including integers and floating-point numbers. The commonly used numeric data types are:

  • int: Represents whole numbers (e.g., -10, 0, 42).
  • double: Represents numbers with decimal points (e.g., 3.14, -0.5).

Example:

int quantity = 10;
double price = 5.99;
2. Strings

Strings are used to represent text. Dart supports both single and double quotes for defining strings.

Example:

String greeting = 'Hello, Dart!';
String company = "MyCompany";
3. Booleans

A Boolean data type represents true or false values. It’s essential for control flow and conditional statements.

Example:

bool isReady = true;
bool isClosed = false;
4. Lists

Lists are collections of ordered objects. Dart provides two primary list types: fixed-length and growable lists.

Example:

List<int> numbers = [1, 2, 3, 4, 5]; // Growable list
List<String> fruits = List(3); // Fixed-length list
fruits[0] = 'Apple';
fruits[1] = 'Banana';
fruits[2] = 'Cherry';
5. Maps

Maps are key-value pairs, where each key is associated with a value. They are highly versatile for organizing and retrieving data.

Example:

Map<String, int> scores = {
  'Alice': 95,
  'Bob': 88,
  'Charlie': 75,
};
6. Sets

Sets are collections of unique objects, making them suitable for maintaining distinct values.

Example:

Set<String> uniqueColors = {'Red', 'Green', 'Blue', 'Red'}; // Only unique values are stored
Dynamic Type

In Dart, you can also use the dynamic data type, which allows a variable to change its data type during runtime. While this flexibility can be powerful, it may lead to runtime errors if not used carefully.

Example:

dynamic dynamicVariable = 42;
dynamicVariable = 'Hello, Dart!';
Type Inference

Dart uses type inference to determine the data type of a variable. This can often simplify code by allowing you to omit explicit type declarations.

Example:

var temperature = 25; // Inferred as int
var title = 'Dart Programming'; // Inferred as String
Conclusion

Variables and data types are fundamental elements in Dart programming. Understanding how to declare variables and work with various data types is essential for building effective Dart applications. Whether you’re dealing with numbers, text, or complex data structures, Dart provides a wide range of data types to suit your needs. It’s important to choose the appropriate data type based on the nature of the data you’re working with and the requirements of your program.