设计模式 单例模式

转自：https://github.com/domnikl/DesignPatternsPHP

final class Singleton
{
    private static ?Singleton $instance = null;

    public static function getInstance(): Singleton
    {
        if (static::$instance === null) {
            static::$instance = new static();
        }

        return static::$instance;
    }

    private function __construct()
    {
    }

    private function __clone()
    {
    }

    private function __wakeup()
    {
    }
}

 

class SingletonTest extends TestCase
{
    public function testUniqueness()
    {
        $firstCall = Singleton::getInstance();
        $secondCall = Singleton::getInstance();

        $this->assertInstanceOf(Singleton::class, $firstCall);
        $this->assertSame($firstCall, $secondCall);
    }
}