yii2源码学习笔记(二十）

Widget类是所有部件的基类。yii2\base\Widget.php

 <?php
 /**
  * @link http://www.yiiframework.com/
  * @copyright Copyright (c) 2008 Yii Software LLC
  * @license http://www.yiiframework.com/license/
  */

 namespace yii\base;

 use Yii;
 use ReflectionClass;

 /**
  * Widget is the base class for widgets.
  * Widget是所有小部件的基类
  * @property string $id ID of the widget. 小部件标识
  * @property \yii\web\View $view The view object that can be used to render views or view files. Note that the
  * type of this property differs in getter and setter. See [[getView()]] and [[setView()]] for details.
  * 用于渲染视图或视图文件的视图对象 在getter 和 setter中是不同的
  * @property string $viewPath The directory containing the view files for this widget. This property is
  * read-only. 包含此控件的视图文件目录
  *
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
 class Widget extends Component implements ViewContextInterface
 {
     /**
      * @var integer a counter used to generate [[id]] for widgets.
      * @internal 用于生成widget ID的计数器
      */
     public static $counter = ;
     /**
      * @var string the prefix to the automatically generated widget IDs.
      * @see getId() 自动生成的前缀
      */
     public static $autoIdPrefix = 'w';
     /**
      * @var Widget[] the widgets that are currently being rendered (not ended). This property
      * is maintained by [[begin()]] and [[end()]] methods. 目前正在渲染的小部件
      * @internal
      */
     public static $stack = [];

     /**
      * Begins a widget.  开始一个部件
      * This method creates an instance of the calling class. It will apply the configuration
      * to the created instance. A matching [[end()]] call should be called later.
      * 将应用配置文件创建调用类的实例，与[end()]方法相对应
      * @param array $config name-value pairs that will be used to initialize the object properties
      * 用于初始化属性的参数
      * @return static the newly created widget instance 静态新创建的部件实例
      */
     public static function begin($config = [])
     {
         $config['class'] = get_called_class();//后期静态绑定类的名称
         /* @var $widget Widget */
         $widget = Yii::createObject($config);//通过类名和传入的配置，实例化调用类
         static::$stack[] = $widget;//将对象放入正在渲染的部件堆栈中

         return $widget;
     }

     /**
      * Ends a widget.   结束小部件
      * Note that the rendering result of the widget is directly echoed out.渲染结果是直接呼应的
      * @return static the widget instance that is ended. 静态结束的部件实例。
      * @throws InvalidCallException if [[begin()]] and [[end()]] calls are not properly nested
      */
     public static function end()
     {
         if (!empty(static::$stack)) {//正在呈现的小部件堆栈中存在调用类实例
             $widget = array_pop(static::$stack);//从堆栈中删除最后一个实例
             if (get_class($widget) === get_called_class()) {
                 echo $widget->run(); //如果删除的实例类名和当前调用类名相同，输出小部件的内容
                 return $widget;
             } else {
                 throw new InvalidCallException("Expecting end() of " . get_class($widget) . ", found " . get_called_class());
             }
         } else {
             throw new InvalidCallException("Unexpected " . get_called_class() . '::end() call. A matching begin() is not found.');
         }
     }

     /**
      * Creates a widget instance and runs it.   创建一个部件实例，并运行
      * The widget rendering result is returned by this method. 返回部件渲染的结果。
      * @param array $config name-value pairs that will be used to initialize the object properties
      * 用于初始化对象属性的参数
      * @return string the rendering result of the widget. 控件的渲染结果。
      */
     public static function widget($config = [])
     {
         ob_start(); //打开输出缓冲区
         ob_implicit_flush(false);//关闭绝对刷新
         /* @var $widget Widget */
         $config['class'] = get_called_class(); //获取调用类的类名
         $widget = Yii::createObject($config);   //实例化类
         $out = $widget->run();//运行部件

         return ob_get_clean() . $out; //返回内部缓冲区的内容，关闭缓冲区
     }

     private $_id;

     /**
      * Returns the ID of the widget. 返回插件的标识
      * @param boolean $autoGenerate whether to generate an ID if it is not set previously
      * 是否生成一个唯一标识，如果没有设置
      * @return string ID of the widget. 部件唯一标识
      */
     public function getId($autoGenerate = true)
     {
         if ($autoGenerate && $this->_id === null) {
             //如果标识为空，并且设置为允许自动生成标识，自动生成
             $this->_id = static::$autoIdPrefix . static::$counter++;
         }

         return $this->_id;
     }

     /**
      * Sets the ID of the widget. 设置小部件标识
      * @param string $value id of the widget. 部件的标识。
      */
     public function setId($value)
     {
         $this->_id = $value;
     }

     private $_view;

     /**
      * Returns the view object that can be used to render views or view files.返回视图对象
      * The [[render()]] and [[renderFile()]] methods will use
      * this view object to implement the actual view rendering.
      * [render()]和[renderFile()]方法用视图对象实现实际的视图显示。
      * If not set, it will default to the "view" application component.
      * @return \yii\web\View the view object that can be used to render views or view files.
      */
     public function getView()
     {
         if ($this->_view === null) {
             $this->_view = Yii::$app->getView();//如果视图对象为空，调用getView()取得视图对象实例
         }

         return $this->_view;
     }

     /**
      * Sets the view object to be used by this widget. 设置当前部件调用的视图对象实例
      * @param View $view the view object that can be used to render views or view files.
      */
     public function setView($view)
     {
         $this->_view = $view;//要用的视图对象
     }

     /**
      * Executes the widget. 执行部件
      * @return string the result of widget execution to be outputted.
      * 控件执行的结果输出。
      */
     public function run()
     {
     }

     /**
      * Renders a view.
      * The view to be rendered can be specified in one of the following formats:
      * 渲染一个视图   实际调用View类中的同名方法 渲染的视图可以用下列方式指定路径
      * - path alias (e.g. "@app/views/site/index");
      * - absolute path within application (e.g. "//site/index"): the view name starts with double slashes.
      *   The actual view file will be looked for under the [[Application::viewPath|view path]] of the application.
      * - absolute path within module (e.g. "/site/index"): the view name starts with a single slash.
      *   The actual view file will be looked for under the [[Module::viewPath|view path]] of the currently
      *   active module.
      * - relative path (e.g. "index"): the actual view file will be looked for under [[viewPath]].
      *
      * If the view name does not contain a file extension, it will use the default one `.php`.
      *
      * @param string $view the view name.   视图名
      * @param array $params the parameters (name-value pairs) that should be made available in the view.
      * 在视图中可用的参数
      * @return string the rendering result. 渲染结果
      * @throws InvalidParamException if the view file does not exist.
      */
     public function render($view, $params = [])
     {
         //调用view类中的render渲染指定的视图
         return $this->getView()->render($view, $params, $this);
     }

     /**
      * Renders a view file. 渲染一个视图文件 同上
      * @param string $file the view file to be rendered. This can be either a file path or a path alias.
      * @param array $params the parameters (name-value pairs) that should be made available in the view.
      * @return string the rendering result.
      * @throws InvalidParamException if the view file does not exist.
      */
     public function renderFile($file, $params = [])
     {
         return $this->getView()->renderFile($file, $params, $this);
     }

     /**
      * Returns the directory containing the view files for this widget. 返回视图文件路径
      * The default implementation returns the 'views' subdirectory under the directory containing the widget class file.
      * @return string the directory containing the view files for this widget.
      */
     public function getViewPath()
     {
         $class = new ReflectionClass($this);
         //取得部件类文件的目录，拼接为视图目录
         return dirname($class->getFileName()) . DIRECTORY_SEPARATOR . 'views';
     }
 }