《大话设计模式》之面向对象和简单工程模式

面向对象

封装

实现一个简单的计算器功能

class Program
{
    public function calculate()
    {
        $number_a = 12;
        $number_b = 5;
        $operate = '+';

        $result = 0;

        switch ($operate) {
            case '+':
                $result = $number_a + $number_b;
                break;

            case '-':
                $result = $number_a - $number_b;
                break;

            case '*':
                $result = $number_a * $number_b;
                break;

            case '/':
                $result = $number_a / $number_b;
                break;

            default:
                # code...
                break;
        }

        echo $number_a . $operate . $number_b .'='. $result;
    }
}

$program = new Program();

$program->calculate();

/**

输出结果：

12+5=17

**/

虽然能够满足需求，但假设另外一个地方也需要用到计算，那么你这部分的代码无法直接被其他人调用，这个时候我们需要对代码进行封装

class Program
{
    public function calculate()
    {
        $number_a = 12;
        $number_b = 5;
        $operate = '+';

        Operation::operate($number_a, $number_b, $operate);
    }
}


class Operation
{

    public static function operate($number_a, $number_b, $operate)
    {
        $result = 0;

        switch ($operate) {
            case '+':
                $result = $number_a + $number_b;
                break;

            case '-':
                $result = $number_a - $number_b;
                break;

            case '*':
                $result = $number_a * $number_b;
                break;

            case '/':
                $result = $number_a / $number_b;
                break;

            default:
                # code...
                break;
        }

        echo $number_a . $operate . $number_b .'='. $result;
    }
}

$program = new Program();

$program->calculate();

/**

输出结果：

12+5=17

**/

对代码进行封装后，不单单自己能调用，其他人也能调用 Operation 类的 operate 方法

而不用去管 Program 类的 calculate 方法里面具体实现了什么方法

Operation::operate(1, 2, '*');

在实际开发中，也需要注意自己当前开发的需求，部分业务逻辑代码能否封装供其他人调用

继承和多态

每个 case 其实都是在做一件事情就是计算，实际开发中每个 case 里面的业务代码肯定不仅仅是一行代码

所以应该再把每个操作进行解耦，这样 Program 类的 calculate 方法只需要调用和传参，并不需要关注每个方法里面具体做了什么操作

通过接口，规范子类实现统一的方法，在类外调用参数修改，而最后的结果也会得到更改来实现多态。

也实现了一个简单的工厂模式，用来解决对象的创建问题

class OperationFathe
{
    public $numberA;
    public $numberB;

}

interface Operation
{
    public function getResult();
    public function log();
}


class OperationAdd extends OperationFathe implements Operation
{
    public function __construct($number_a, $number_b)
    {
        $this->numberA = $number_a;
        $this->numberB = $number_b;
    }

    public function getResult()
    {
        return $this->numberA + $this->numberB;
    }

    public function log()
    {
        echo '调用了加法:';
    }
}

class OperationSub extends OperationFathe implements Operation
{
    public function __construct($number_a, $number_b)
    {
        $this->numberA = $number_a;
        $this->numberB = $number_b;
    }

    public function getResult()
    {
        return $this->numberA - $this->numberB;
    }

    public function log()
    {
        echo '调用了减法:';
    }
}

class OperationMul extends OperationFathe implements Operation
{
    public function __construct($number_a, $number_b)
    {
        $this->numberA = $number_a;
        $this->numberB = $number_b;
    }

    public function getResult()
    {
        return $this->numberA * $this->numberB;
    }

    public function log()
    {
        echo '调用了乘法:';
    }
}


class OperationDiv extends OperationFathe implements Operation
{
    public function __construct($number_a, $number_b)
    {
        $this->numberA = $number_a;
        $this->numberB = $number_b;
    }

    public function getResult()
    {
        return $this->numberA / $this->numberB;
    }

    public function log()
    {
        echo '调用了除法:';
    }
}

class Program
{
    public function factory($number_a, $number_b, $operate)
    {
        switch ($operate) {
            case '+':
                $obj = new OperationAdd($number_a, $number_b);
                break;

            case '-':
                $obj = new OperationSub($number_a, $number_b);
                break;

            case '*':
                $obj = new OperationMul($number_a, $number_b);
                break;

            case '/':
                $obj = new OperationDiv($number_a, $number_b);
                break;

            default:
                # code...
                break;
        }

        return $obj;
    }
}


$number_a = 12;
$number_b = 5;
$operate = '+';

$program = new Program();
$obj = $program->factory($number_a, $number_b, $operate);
$obj->log();
echo $obj->getResult();

/**

输出结果：

调用了加法:17

**/