依赖注入

依赖注入(DI)指的就是当你需要实例化的类依赖于其他类的实现的时候；

不需要在本类中实例化所依赖的类，而是将所依赖的类通过参数的形式传入 即构造注入(构造函数)和设值注入(set方法);

高耦合的反例

//高耦合

class Apple
{
​    protected $name =  ‘ ‘;

    public function construct()
    {
        $this- >name =  ‘Apple ‘;
    }

    public function getName()
    {
        return $this- >name;
    }
}

class Orange
{
​    protected $name =  ‘ ‘;

    public function construct()
    {
        $this- >name =  ‘Orange ‘;
    }

    public function getName()
    {
        return $this- >name;
    }
}

class Person
{
​    protected $likeFood =  ‘ ‘;

    public function construct()
    {
        $this- >likeFood = new Orange();
        echo  ‘这个人喜欢吃 ‘ . $this- >likeFood- >getName();
    }
}

new Person();

低耦合注入

//低耦合实现
interface Fruit
{
​    public function getName();

}

class Apple implements Fruit
{
​    protected $name =  ‘ ‘;

    public function construct()
    {
        $this- >name =  ‘Apple ‘;
    }

    public function getName()
    {
        return $this- >name;
    }
}

class Orange implements Fruit
{
​    protected $name =  ‘ ‘;

    public function construct()
    {
        $this- >name =  ‘Orange ‘;
    }

    public function getName()
    {
        return $this- >name;
    }
}

class Person
{
​    public $likeFood;

    public function construct(Fruit $fruit)
    {
        echo  ‘这个人喜欢吃 ‘ . $fruit- >getName();
    }
}

$apple = new Apple();
new Person($apple);