Object-Oriented Programming (OOP) in Dart

Definition

Object-Oriented Programming is a way to organize code using objects and classes. Classes are templates that define what data (properties) and actions (methods) an object should have.

Core Concepts

Class

A blueprint or template for creating objects.

Defines properties (data)

Defines methods (functions)

One class can create many objects

Object (Instance)

A specific copy created from a class.

Has its own property values

Can call class methods

Created with the `new` keyword (or just the class name in Dart)

Properties

Variables that belong to an object.

Store data about the object

Each object has its own copy

Accessed with dot notation: `object.property`

Methods

Functions that belong to a class.

Actions an object can perform

Called with dot notation: `object.method()`

Example Structure

class ClassName {

// Properties

type propertyName;

// Methods

returnType methodName(parameters) {

// method body

}

// Create an object

ClassName obj = ClassName();

obj.propertyName = value;

obj.methodName();

Cell2Dart

// Simple class with properties class Person { String name = ''; int age = 0; } // Create a Person object Person person = Person(); person.name = 'Alice'; person.age = 30; print('${person.name} is ${person.age} years old'); // Create another object Person person2 = Person(); person2.name = 'Bob'; person2.age = 25; print('${person2.name} is ${person2.age} years old');

Memory: Stack vs Heap

Stack Memory

Stores simple variables (int, String, bool, double)

Stores references (memory addresses) to objects

Fast but limited size

Heap Memory

Stores actual objects

Objects live here after creation

Can be large but managed by garbage collector

When you create an object:

1. A reference is created on the stack

2. The actual object is created on the heap

3. The reference points to the object on the heap

Cell4Dart

// Class with methods class Car { String brand = ''; String color = ''; void describe() { print('A $color $brand'); } } // Create and use objects Car car1 = Car(); car1.brand = 'Tesla'; car1.color = 'Red'; car1.describe(); Car car2 = Car(); car2.brand = 'BMW'; car2.color = 'Blue'; car2.describe();

Practice

CellcustomDart

class Car { String brand = ''; String color = ''; } Car myCar = Car(); myCar.brand = 'Tesla'; myCar.color = 'Red'; print('${myCar.color} ${myCar.brand}');

OOP in Dart