PHP-dä OOP-dä zynjyrlarda howpsuz çykaryş operatorunyň ulanmagy

Howpsuz çykaryş operatory ?-> çaýryş zynjyrlarynda ulanylyp bilner. Bir mysalda göreris. Aşakdaky synplarymyz bolsun:

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

User-iň şäherini zynjyr arkaly almak isleýändigimizi göz öňünde tutalyň:

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

Eger şäher null deň bolsa, onda şeýle zynjyryň çaýrylmagy ýalňyşlyga getirer:

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

Ýalňyşlygy basyp ýatyrmak üçin, biz howpsuz çykaryş operatoryny ulanyp bileris:

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

Indi şäherem null bolup bilýändigini göz öňünde tutalyň. Bu ýagdaýda howpsuz çykaryş operatoruny iki gezek ulanyp bileris:

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

Aşakdaky kody howpsuz çykaryş operatory arkaly gowulandyryň:

<?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('developer');
	$employee = new Employee('john', $position);
	
	echo $employee->position->getName();
?>