PHP da OOP da Zanjirlarda Xavfsiz Olish Operatori

Xavfsiz olish operatori ?-> chaqirish zanjirlarida qo'llanilishi mumkin. Keling, bir misol orqali ko'rib chiqaylik. Faraz qilaylik, bizda quyidagi klasslar mavjud:

<?php
	class User {
		public $city = null;
	}
	
	class City {
		public function getName() {
			return 'shahar nomi';
		}
	}
?>

Faraz qilaylik, biz foydalanuvchi shahrini zanjir orqali olishni istaymiz:

<?php
	$user = new User();
	$user->city = new City();
	
	echo $user->city->getName();
?>

Agar shahar null bo'lsa, bunday zanjirni chaqirish xatolikka olib keladi:

<?php
	$user = new User();
	$user->city = null;
	
	echo $user->city->getName(); // xatolik
?>

Xatolikni oldini olish uchun biz xavfsiz olish operatoridan foydalanishimiz mumkin:

<?php
	$user = new User();
	$user->city = null;
	
	echo $user->city?->getName();
?>

Endi faraz qilaylik, shahar ham null bo'lishi mumkin. Bunday holda biz xavfsiz olish operatorini ikki marta ishlatishimiz mumkin:

<?php
	$user = null;
	
	echo $user?->city?->getName();
?>

Quyidagi kodni xavfsiz olish operatori orqali yaxshilang:

<?php
	class Employee {
		public $name;
		public $position;
		
		public function __construct($name, $position)
		{
			$this->name = $name;
			$this->position = $position;
		}
	}
	
	class Position {
		private $name;
		
		public function __construct($name)
		{
			$this->name = $name;
		}
		
		public function getName() {
			return $this->name;
		}
	}
	
	$position = new Position('dasturchi');
	$employee = new Employee('john', $position);
	
	echo $employee->position->getName();
?>