PHP Design Pattern Decorator Pattern_PHP Tutorial

php design pattern decorator pattern

1. Introduction

1. Decorator mode (Decorator), which can dynamically add and modify the function of a class
2. A class provides a function. If you want to modify and add additional functions, in the traditional programming mode, you need to write a subclass to inherit it and reimplement the class method
3. Using the decorator mode, you only need to add a decorator object at runtime, which can achieve maximum flexibility.

2. Example

Next, let’s give an example of using PHP to implement the function of a small drawing board (drawing graphics of specified colors)

1. The traditional way before using decorators

1. Implement a drawing board class

<code class="language-php" hljs="">
<!--?php

    class Canvas
    {
        //保存点阵的一个数组
        public $data;

        //初始化点阵
        function init ( $width = 20, $height = 10 )
        {
            $data = array();
            for ($i = 0; $i < $height; $i++) {
                for ($j = 0; $j < $width; $j++) {
                    $data[ $i ][ $j ] = '*';
                }
            }
            $this--->data = $data;
        }

        //初始化一个正方形的点阵
        function rect ( $a1, $a2, $b1, $b2 )
        {
            foreach ($this->data as $k1 => $line) {
                if ($k1 < $a1 or $k1 > $a2)
                    continue;
                foreach ($line as $k2 => $char) {
                    if ($k2 < $b1 or $k2 > $b2)
                        continue;
                    $this->data[ $k1 ][ $k2 ] = &#39;  &#39;;
                }
            }
        }

        //开始执行画图
        function draw ()
        {
            foreach ($this->data as $line) {
                foreach ($line as $char) {
                    echo $char;
                }
                echo 

;
            }
        }
    }</code>

2. Call

<code class="language-php" hljs="">$canvas = new Canvas();
$canvas->init(40, 20);

$canvas->rect(4,15,9,30);
$canvas->draw();</code>

3. Result We see the following square

<code class="language-php" hljs="">****************************************
****************************************
****************************************
****************************************
****************************************
*********                      *********
*********                      *********
*********                      *********
*********                      *********
*********                      *********
*********                      *********
*********                      *********
*********                      *********
*********                      *********
*********                      *********
****************************************
****************************************
****************************************
****************************************
****************************************</code>

4. Here comes the next question

What if I want to add the color I want to this graphic?

5. Solve the above problems (output the html code when displaying, modify the draw method and you can see the results you want)

<code class="language-php" hljs="">        //开始执行画图
        function draw ()
        {
            echo </code>

; foreach ($this->data as $line) { foreach ($line as $char) { echo $char; } echo<code class="language-php" hljs="">; foreach ($this->data as $line) { foreach ($line as $char) { echo $char; } echo<br> ; } echo ; } echo

; }

6. The problem comes again

1. It is hard-coded like this. If I don’t want to add color that day, but I want to make it bold or italic, then I need to modify the code, or I want to add a title on it. . . Waiting for the demand, let's use the decorator mode to modify the above code to decouple the above code!

2. Use the decorator mode to implement the above functions

1. Implement a decorator base class

<code class="language-php" hljs="">//画图装饰器
interface DrawDecorator
{
    //画之前的操作
    function beforeDraw();

    //画之后的操作
    function afterDraw();
}</code>

2. Implement a color decorator

<code class="language-php" hljs="">class ColorDrawDecorator implements DrawDecorator
{
    //颜色属性
    protected $color;

    //初始化颜色
    function __construct($color = &#39;red&#39;)
    {
        $this->color = $color;
    }

    //画之前的操作
    function beforeDraw()
    {
        echo </code>

; } //画之后的操作 function afterDraw() { echo

; } }

3. Re-implement the drawing board class

<code class="language-php" hljs="">
    class Canvas
    {
        //保存点阵的一个数组
        public $data;

        //保存装饰器对象
        protected $decorators = array();

        //初始化点阵
        function init($width = 20, $height = 10)
        {
            $data = array();
            for($i = 0; $i < $height; $i++)
            {
                for($j = 0; $j < $width; $j++)
                {
                    $data[$i][$j] = &#39;*&#39;;
                }
            }
            $this->data = $data;
        }

        //注册装饰器对象
        function addDecorator(DrawDecorator $decorator)
        {
            $this->decorators[] = $decorator;
        }

        //画之前的操作
        function beforeDraw()
        {
            foreach($this->decorators as $decorator)
            {
                $decorator->beforeDraw();
            }
        }

        //画之后的操作
        function afterDraw()
        {
            $decorators = array_reverse($this->decorators);
            foreach($decorators as $decorator)
            {
                $decorator->afterDraw();
            }
        }

        //开始画图
        function draw()
        {
            $this->beforeDraw();
            foreach($this->data as $line)
            {
                foreach($line as $char)
                {
                    echo $char;
                }
                echo 

;
            }
            $this->afterDraw();
        }

        //描述一个矩形的点阵
        function rect($a1, $a2, $b1, $b2)
        {
            foreach($this->data as $k1 => $line)
            {
                if ($k1 < $a1 or $k1 > $a2) continue;
                foreach($line as $k2 => $char)
                {
                    if ($k2 < $b1 or $k2 > $b2) continue;
                    $this->data[$k1][$k2] = &#39; &#39;;
                }
            }
        }
    }</code>

4. Call

<code class="language-php" hljs="">$canvas = new Canvas();
//注入装饰器对象
$canvas->addDecorator(new ColorDrawDecorator(&#39;green&#39;));
$canvas->init(40, 20);

$canvas->rect(4,15,9,30);
$canvas->draw();</code>

5. Results

Output a green rectangle

Similarly, if you also want to use bolding, italics, set custom titles, etc., just create a specific decorator and inject it into the canvas.

6. Summary

1. The decorator is to add some of your customized operations before performing a specific operation
2. The implementation of decorators is like a hook mechanism, such as the hook mechanism in drupal
3. The decorator mechanism can also be implemented using call_user_func or call_user_func_array. You can refer to Drupal’s hook implementation for this, which is also pretty good! I won’t introduce it here because it is not within the design pattern. I will write about it later when I have time.

http://www.bkjia.com/PHPjc/1036924.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/1036924.htmlTechArticlephp design mode Decorator mode 1. Introduction 1. Decorator mode (Decorator), which can be dynamically added and modified Function of class 2. A class provides a function. If you want to modify and add...