PHP行为设计模式之策略模式

<?php
interface MathStrategy
{
    public function calculate(int $a, int $b): int;
}
class Addition implements MathStrategy
{
    public function calculate(int $a, int $b): int
    {
        return $a + $b;
    }
}
class Multiplication implements MathStrategy
{
    public function calculate(int $a, int $b): int
    {
        return $a * $b;
    }
}
class MathContext
{
    private $strategy;
    public function __construct(MathStrategy $strategy)
    {
        $this->strategy = $strategy;
    }
    public function setStrategy(MathStrategy $strategy): void
    {
        $this->strategy = $strategy;
    }
    public function calculate(int $a, int $b): int
    {
        return $this->strategy->calculate($a, $b);
    }
}
$context = new MathContext(new Addition());
echo $context->calculate(2, 3) . "\n"; // output: 5
$context->setStrategy(new Multiplication());
echo $context->calculate(2, 3) . "\n"; // output: 6