dart object oriented programming language
dart object oriented programming language

A dart is a programming language that support all the concepts of object oriented programming such as:

  • Classes
  • Objects
  • Inheritance
  • Polymorphism
  • Interface
  • Abstract class

The main goal of oops concepts in dart is to reduce programming complexity & can execute many tasks at once.

Let’s have a brief introduction of dart oops concepts one by one

1. Classes

Classes are a user defined datatype that describe how an object should behave.

A dart class is a blueprint by which we can create an object to access properties members of a class.

A class in dart can contain:

  • fields.
  • Methods (<gettter>/<setter>).
  • Constructors.
  • User Defined Methods/functions.

Syntax of dart class:

class class_name{
  methods or functions

Example below

2. Object

A object is an Instance of a class, so as you know, A Class is a blueprint from which object are created.

A dart object is a logical entity & Physical entity.

Object in dart can be easily understood by taking real-life object such as : Pen, Table, Car, Table etc.

In Dart Object of a class is created by below syntax:


Class_name object_name = Class_name();

Note: In dart there is no need to use new keywork to create a object.

For Easy understanding, class & object in dart let’s take a example of a car.

A Car has a brandName, model_no, color, price, topSpeed, Therefore we have various brands of cars & each car will have a individual properties like name, color and all…

Therefore here each car is an object that is created by using a class.

Dart Class & Object Example – OOPS

Dart Car Program

class Car{

  // data members
  String? brandName;
  String? modelNo;
  String? color;
  int? speed;
  int? price;

   Car(String brandName,String modelNo,String color,int speed,int price){
       this.brandName = brandName;
       this.modelNo = modelNo;
       this.color = color;
       this.speed = speed;
       this.price =price;

void main(){
  print("Hello World");

   //creating call object by passing value using parameter constructor
    Car audi = Car('Audi','A6','RED',300,5000000);

    // using object we can access class properties using dot . operator
     print('Name: ${audi.brandName}');
    print('Model No: ${audi.modelNo}');
    print('Car Color: ${audi.color}');
    print('Car Speed: ${audi.speed}');
    print('Car Price ${audi.price}');

Dart program to calculate age using data of birth

We will create a class, that will calculate & find the exact age of a person using data of birth.

Here is below dart class & object program, we have 3 properties: datatype, constructor, & a method.

  • dataType: Used to hold the data in variable eg: String webSite = ‘Proto Coders Point‘;
  • constructor: we have parametrized constructor that except 2 parameter (name & date of birth).
  • method: That calculate age using date_of_birth(dob) & print the age on console.

Dart code below:

void main(){
  print("Hello World");
    //create a object by passing value to constructor of class.
    AgeFinderClass myClassObject = AgeFinderClass('Rajat Palankar', DateTime(19XX, X, X));  // pass your dob here : (1999,5,6)

    //calling a method in class using object


// dart class 
class AgeFinderClass {
  String name;
  DateTime? date_of_birth;

  // Constructor
  AgeFinderClass(this.name, this.date_of_birth);

  // Method.
  void calculate() {
    print('Name:  $name');
    var date_of_birth = this.date_of_birth;
    if (date_of_birth != null) {
      int years = DateTime.now().difference(date_of_birth).inDays ~/ 365;
      print('Your Age is: $years');

3. Inheritance in dart

Inheritance is one of the pillar of object oriented. Inheritance in dart, is very important concepts of OOPS, By using dart Inheritance, we can derive/acquire all the method & behaviour of a parent class.

Eg: Real Life Example

You dad, build house, earn money, has a car, bike & a business, Therefore you have all the rights to use all of his properties.

Inheritance represent the IS-A relationship also been called as parent-child relationship.

Why do we use Inheritance in dart

It’s been used to re-use the method & field of a parent class.

  • Code Reusability
  • Method Overriding (Polymorphism)

Syntax of dart class inheritance

class child-class-name extends parent_class_name{
      //method & field


Single Inheritance Example

In below example we have 2 class ‘Animal’ & ‘Dog’.

Dog acquire all the properties of Animal class by extending it,

Therefore, now Dog can use Animal class eat() method.

class Animal{
  void eat(){

class Dog extends Animal{
  void dark(){
void main(){
  Dog d = Dog();  // here d is object of Dog Class
  d.eat();     // dog can use Animal class method

4. Polymorphism in dart

In Dart or any OOPS concept a polymorphism is a feature that perform different action in different situation.

Polymorphism definition says:- A ability of an object to take on many forms, An example of polymorphism is when a parent class refer to child class object.

Real Life example

Let’s take an example to understand polymorphism. A person have many characteristics & perform different roles in his life, He can be a dad, husband, a employee or a business man, so as you saw, The same person plays different roles in different situation. This is the best & easiest way to understand what is polymorphism in dart.

Here poly means many, & morph means forms.

Dart polymorphism example

void main() {
  // parent class object creation
  Animal ma ;
  // using parent object, re-initialize subsclass object
  ma =  Dog();
  // class method 
  print('Dog making sound: ${ma.makeSound()}');
  ma = Cat();
  print("Cat :- "+ma.makeSound());
  ma = Bird();
   print("Crow Making sound :- "+ma.makeSound());

class Animal{
    return "Animal Sound is not Defined";

class Dog extends Animal{
   String makeSound(){
    return "bow wow";

class Cat extends Animal{
   //no sound method declared // so it will take sound property from parent class "Animal"

class Bird extends Animal{
  String makeSound(){
    return "AWW! AWW!";


In above code, we have a super class i.e Animal which has method makeSound(), Then we have a sub class i.e Dog, Cat, Bird. They have their own sound i.e method implemented to make respective animal sound.

In above code, I have defined sound method for Dog & Bird but not Cat, Therefore when cats makeSound() method is class, it will refer it parent method i.e. superclass Animal & makeSound() “sound is not defined”.

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