php_demo/07面向对象/21协变和逆变/02逆变.php

<?php
    //逆变
    class Food{}

    class AnimalFood extends Food{}

    abstract class Animal{
        protected string $name;

        public function __construct(string $name){
            $this->name=$name;
        }

        public function eat(AnimalFood $food){
            echo $this->name."eats".get_class($food);
        }
    }

    class Dog extends Animal{
        public function eat(Food $food){
            echo $this->name."eats".get_class($food);
        }
    }

    $kitty=(new CatShelter)->adopt("ricky");
    $catFood=new AnimalFood();
    $kitty->eat($catFood).PHP_EOL;

    $doggy=(new DogShelter)->adopt("lucky");
    $banana=new Food();
    $doggy->eat($banana);
?>