Opereta ya Uchimbaji Salama katika Minyororo katika OOP katika PHP

Opereta ya uchimbaji salama ?-> inaweza kutumiwa katika minyororo ya miito. Tuangalie kwa mfano. Tuchukulie tuna madarasa yafuatayo:

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

Tuchukulie tunataka kupata mji wa mtumiaji kupitia mnyororo:

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

Iwapo mji unakuwa sawa na null, basi utoaji wa mnyororo kama huo utasababisha hitilafu:

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

Ili kukandamiza hitilafu, tunaweza kutumia opereta ya uchimbaji salama:

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

Tuchukulie sasa mji pia unaweza kuwa null. Katika hali hii tunaweza kutumia opereta ya uchimbaji salama mara mbili:

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

Boresha msimbo ufuatao kupitia opereta ya uchimbaji salama:

<?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();
?>