PHP vorislik (inheritance)
PHP - Meros
PHP OOP-da meros olish bolalar classiga ota-classdan barcha umumiy va himoyalangan xususiyatlar va usullarni meros qilib olish imkonini beradi. Bundan tashqari, bolalar classining o‘ziga xos xususiyatlari va metodlari bo‘lishi mumkin.
Eslatma: Ota-classning shaxsiy usullaridan bolalar classiga kira olmaydi.
Meroslangan class
extends bilan aniqlanadi
kalit so‘z.
Quyidagi misolda Qulupnay classi Fruit classidan meros qilib olingan. Bu Strawberry klassi umumiy $name va $color xususiyatlaridan, shuningdek Fruit sinfidagi umumiy __construct() va intro() usullaridan (meros tufayli) foydalanishi mumkinligini anglatadi. Qulupnay classining ham o‘z usuli bor: message():
Misol
<?php
// Parent class
class Fruit {
public $name;
public $color;
public function __construct($name, $color) {
$this->name = $name;
$this->color = $color;
}
public function intro() {
echo "The fruit is $this->name and the color is $this->color.<br>";
}
}
// Strawberry is inherited from Fruit
class Strawberry extends Fruit {
public function message() {
echo "Am I a fruit or a berry? ";
}
}
$strawberry = new Strawberry("Strawberry", "red");
$strawberry->intro();
$strawberry->message();
?>
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PHP - Meros va himoyalangan kirish modifikatori
Oldingi bobda biz
protected
xususiyatlari yoki metodlari mumkin
doirasida kirish mumkin
class va shu classdan olingan classlar bo‘yicha. U nimani anglatadi?
Keling, bir misolni ko‘rib chiqaylik:
Misol
<?php
class Fruit {
public $name;
public $color;
public function __construct($name, $color) {
$this->name = $name;
$this->color = $color;
}
protected function intro() {
echo "The fruit is $this->name and the color is $this->color.";
}
}
class Strawberry extends Fruit {
public function message() {
echo "Am I a fruit or a berry? ";
}
}
// Try to call all three methods from outside class
$strawberry = new Strawberry("Strawberry", "red"); // OK. __construct() is public
$strawberry->message(); // OK. message() is public
$strawberry->intro(); // ERROR. intro() is protected
?>
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Yuqoridagi misolda, agar biz
protected metodini (intro()) sinfdan tashqarida chaqirmoqchi bo‘lsak, xatoga duch kelishimizni ko‘ramiz.
public
metod yaxshi ishlaydi!
Keling, yana bir misolni ko‘rib chiqaylik:
Misol
<?php
class Fruit {
public $name;
public $color;
public function __construct($name, $color) {
$this->name = $name;
$this->color = $color;
}
protected function intro() {
echo "The fruit is $this->name and the color is $this->color.";
}
}
class Strawberry extends Fruit {
public function message() {
echo "Am I a fruit or a berry? ";
// Call protected method from within derived class - OK
$this -> intro();
}
}
$strawberry = new Strawberry("Strawberry", "red"); // OK. __construct() is public
$strawberry->message(); // OK. message() is public and calls intro() (which is protected) from within the derived class
?>
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Yuqoridagi misolda biz hamma narsa yaxshi ishlayotganini ko‘ramiz! Buning sababi, biz chaqiramiz
protected
usuli (intro()) olingan class ichidan.
PHP - Meroslangan usullarni bekor qilish
Usullarni qayta belgilash orqali meros qilib olingan usullarni bekor qilish mumkin (xuddi shunday foydalaning ism) bolalar classida.
Quyidagi misolga qarang. Bolalar sinfidagi (Strawberry) __construct() va intro() metodlari ota-sinfdagi (Fruit) __construct() va intro() usullarini bekor qiladi:
Misol
<?php
class Fruit {
public $name;
public $color;
public function __construct($name, $color) {
$this->name = $name;
$this->color = $color;
}
public function intro() {
echo "The fruit is $this->name and the color is $this->color.";
}
}
class Strawberry extends Fruit {
public $weight;
public function __construct($name, $color, $weight) {
$this->name = $name;
$this->color = $color;
$this->weight = $weight;
}
public function intro() {
echo "A $this->name is $this->color, and the weight is $this->weight gram.";
}
}
$strawberry = new Strawberry("Strawberry", "red", 50);
$strawberry->intro();
?>
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PHP - yakuniy kalit so‘z
final
kalit so‘z class merosini oldini olish yoki usulni bekor qilishni oldini olish uchun ishlatilishi mumkin.
Quyidagi misol class merosini qanday oldini olish mumkinligini ko‘rsatadi:
Misol
<?php
final class Fruit {
// some code
}
// will result in error
class Strawberry extends Fruit {
// some code
}
?>
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Quyidagi misol usulni bekor qilishni qanday oldini olishni ko‘rsatadi:
Misol
<?php
class Fruit {
final public function intro() {
// some code
}
}
class Strawberry extends Fruit {
// will result in error
public function intro() {
// some code
}
}
?>
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