Tag: Oops

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Inheritance

PHP Tutorial

Control Statement

PHP Functions

PHP Arrays

PHP Strings

PHP Math

PHP Form

PHP Include

State Management

PHP File

Upload Download

PHP OOPs Concepts

PHP MySQLi

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PHP Mail

It is a concept of accessing the features of one class from another class. If we inherit the class features into another class, we can access both class properties. We can extends the features of a class by using ‘extends’ keyword.

  • It supports the concept of hierarchical classification.
  • Inheritance has three types, single, multiple and multilevel Inheritance.
  • PHP supports only single inheritance, where only one class can be derived from single parent class.
  • We can simulate multiple inheritance by using interfaces.

Example 1

<?php  
class a  
    {  
        function fun1()  
        {  
            echo "protutorials";  
        }  
    }  
    class b extends a  
    {  
        function fun2()  
        {  
            echo "SSSIT";  
        }  
    }  
    $obj= new b();  
    $obj->fun1();  
?>

Output:

protutorials

Example 2

<?php  
    class demo  
    {  
        public function display()  
        {  
            echo "example of inheritance  ";  
        }     
    }  
    class demo1 extends demo  
    {  
        public function view()  
        {  
            echo "in php";  
        }     
    }  
    $obj= new demo1();  
    $obj->display();  
    $obj->view();  
?>

Output:

example of inheritance in php

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PHP With OOPS Concept

PHP Tutorial

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PHP Strings

PHP Math

PHP Form

PHP Include

State Management

PHP File

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PHP OOPs Concepts

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PHP Topics

PHP Mail

Object-oriented programming is a programming model organized around Object rather than the actions and data rather than logic.

Class:

A class is an entity that determines how an object will behave and what the object will contain. In other words, it is a blueprint or a set of instruction to build a specific type of object.

In PHP, declare a class using the class keyword, followed by the name of the class and a set of curly braces ({}).

This is the blueprint of the construction work that is class, and the houses and apartments made by this blueprint are the objects.

Syntax to Create Class in PHP

  1.   
<?php  
class MyClass  
    {  
        // Class properties and methods go here  
    }  
?>

Important note:

In PHP, to see the contents of the class, use var_dump(). The var_dump() function is used to display the structured information (type and value) about one or more variables.

Syntax:

  1. var_dump($obj);  

Object:

A class defines an individual instance of the data structure. We define a class once and then make many objects that belong to it. Objects are also known as an instance.

An object is something that can perform a set of related activities.

Syntax:

  

<?php  
class MyClass  
{  
        // Class properties and methods go here  
}  
$obj = new MyClass;  
var_dump($obj);  
?>

Example of class and object:

<?php  
class demo  
{  
        private $a= "hello tutorialspro";  
        public function display()  
        {  
        echo $this->a;  
        }  
}  
$obj = new demo();  
    $obj->display();  
?>

Output:

hello tutorialspro

Example 2: Use of var_dump($obj);

  

<?php  
class demo  
{  
        private $a= "hello javatpoint";  
        public function display()  
        {  
        echo $this->a;  
        }  
}  
$obj = new demo();  
    $obj->display();  
    var_dump($obj);  
?>

Output:

hello tutorialspro

object(demo)[1]

private ‘a’ => string ‘hello tutorialspro’ (length=18)

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Kotlin Class and Objects

Kotlin Introduction

Kotlin Flow Control

Kotlin Functions

Kotlin OOP

In this article, you’ll be introduced to Object-oriented programming in Kotlin. You’ll learn what a class is, how to create objects and use it in your program.

Kotlin supports both functional and object-oriented programming.

Kotlin supports features such as higher-order functions, function types and lambdas which makes it a great choice for working in functional programming style. You will learn about these concept in later chapters. This article will focus on object-oriented style of programming in Kotlin.

Object-oriented Programming (OOP)

In object-oriented style of programming, you can divide a complex problem into smaller sets by creating objects.

These objects share two characteristics:

  • state
  • behavior

Let’s take few examples:

  1. Lamp is an object
    • It can be in on or off state.
    • You can turn on and turn off lamp (behavior).
  2. Bicycle is an object
    • It has current gear, two wheels, number of gear etc. states.
    • It has braking, accelerating, changing gears etc. behavior.

You will learn about detail features of an object-oriented programming like: data encapsulation, inheritance and polymorphism as we go on. This article will focus on the basics to keep things simple.

Kotlin Class

Before you create objects in Kotlin, you need to define a class.

A class is a blueprint for the object.

We can think of class as a sketch (prototype) of a house. It contains all the details about the floors, doors, windows etc. Based on these descriptions we build the house. House is the object.

Since, many houses can be made from the same description, we can create many objects from a class.

How to define a class in Kotlin?

To define a class in Kotlin, class keyword is used:

class ClassName {
    // property
    // member function
    ... .. ...
}

Here’s an example:

class Lamp {

    // property (data member)
    private var isOn: Boolean = false

    // member function
    fun turnOn() {
        isOn = true
    }

    // member function
    fun turnOff() {
        isOn = false
    }
}

Here, we defined a class named Lamp.

The class has one property isOn (defined in same way as variable), and two member functions turnOn() and turnOff().

In Kotlin, either the property must be initialized or must be declared abstract (Visit: Kotlin Abstract Class to learn more). In the above example, isOn property is initialized to false.

Classes, objects, properties, member function etc. can have visibility modifiers. For example, the isOn property is private. This means, the isOn property can be changed from only inside the Lamp class.

Other visibility modifiers are:

  • private – visible (can be accessed) from inside the class only.
  • public – visible everywhere.
  • protected – visible to the class and its subclass.
  • internal – any client inside the module can access them.

You will learn about protected and internal modifiers later in Kotlin visibility modifiers article.

If you do not specify the visibility modifier, it will be public by default.

In the above program, turnOn() and turnOff() member functions are public whereas, isOn property is private.

Kotlin Objects

When class is defined, only the specification for the object is defined; no memory or storage is allocated.

To access members defined within the class, you need to create objects. Let’s create objects of Lamp class.

class Lamp {

    // property (data member)
    private var isOn: Boolean = false

    // member function
    fun turnOn() {
        isOn = true
    }

    // member function
    fun turnOff() {
        isOn = false
    }
}

fun main(args: Array<String>) {

    val l1 = Lamp() // create l1 object of Lamp class
    val l2 = Lamp() // create l2 object of Lamp class
}

This program creates two objects l1 and l2 of class Lamp. The isOn property for both lamps l1 and l2 will be false.

How to access members?

You can access properties and member functions of a class by using . notation. For example,

l1.turnOn()

This statement calls turnOn() function for l1 object.

Let’s take another example:

l2.isOn = true

Here, we tried to assign true to isOn property of l2 object. Note that, isOn property is private, and if you try to access isOn from outside the class, an exception is thrown.

Example: Kotlin Class and Object

class Lamp {

    // property (data member)
    private var isOn: Boolean = false

    // member function
    fun turnOn() {
        isOn = true
    }

    // member function
    fun turnOff() {
        isOn = false
    }

    fun displayLightStatus(lamp: String) {
        if (isOn == true)
            println("$lamp lamp is on.")
        else
            println("$lamp lamp is off.")
    }
}

fun main(args: Array<String>) {

    val l1 = Lamp() // create l1 object of Lamp class
    val l2 = Lamp() // create l2 object of Lamp class

    l1.turnOn()
    l2.turnOff()

    l1.displayLightStatus("l1")
    l2.displayLightStatus("l2")
}

When you run the program, the output will be:

l1 Lamp is on.
l2 Lamp is off.

In the above program,

  • Lamp class is created.
  • The class has a property isOn and three member functions turnOn(), turnOff() and displayLightStatus().
  • Two objects l1 and l2 of Lamp class are created in the main() function.
  • Here, turnOn() function is called using l1 object: l1.turnOn(). This method sets isOn instance variable of l1 object to true.
  • And, turnOff() function is called using l2 object: l1.turnOff(). This method sets isOff instance variable of l2 object to false.
  • Then, displayLightStatus() function is called for l1 and l2 objects which prints appropriate message depending on whether isOn property is true or false.

Notice that, the isOn property is initialized to false inside the class. When an object of the class is created, isOn property for the object is initialized to false automatically. So, it’s not necessary for l2 object to call turnOff() to set isOn property to false.

For example:

class Lamp {

    // property (data member)
    private var isOn: Boolean = false

    // member function
    fun turnOn() {
        isOn = true
    }

    // member function
    fun turnOff() {
        isOn = false
    }

    fun displayLightStatus() {
        if (isOn == true)
            println("lamp is on.")
        else
            println("lamp is off.")
    }
}

fun main(args: Array<String>) {

    val lamp = Lamp()
    lamp.displayLightStatus()
}

When you run the program, the output will be:

lamp is off.
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