每日一题

什么是依赖注入？

• 不依赖自身，从外界注入

---

示例

<?php
    namespace Database;

    class Database
    {
        protected $adapter;

        public function __construct(MySqlAdapter $adapter)
        {
            $this->adapter = $adapter;
        }
    }

    class MysqlAdapter {}
?>

什么是依赖反转准则？

• 依赖于抽象而不是具体

<?php
    namespace Database;

    class Database
    {
        protected $adapter;

        public function __construct(AdapterInterface $adapter)
        {
            $this->adapter = $adapter;
        }
    }

    interface AdapterInterface {}

    class MysqlAdapter implements AdapterInterface {}


?>