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 = 0;
    /**
     * @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';
    }
}