View类

View继承了component，用于渲染视图文件

yii2\base\View.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 yii\helpers\FileHelper;use yii\widgets\Block;use yii\widgets\ContentDecorator;use yii\widgets\FragmentCache;/** * View represents a view object in the MVC pattern. * MVC中的视图 * View provides a set of methods (e.g. [[render()]]) for rendering purpose. * 视图提供了一套渲染页面的方法 * @property string|boolean $viewFile The view file currently being rendered. False if no view file is being * rendered. This property is read-only. * * @author Qiang Xue <[e-mail]> * @since 2.0 */class View extends Component{    /**     * @event Event an event that is triggered by [[beginPage()]].     * 事件被[beginPage()]触发     */    const EVENT_BEGIN_PAGE = 'beginPage';    /**     * @event Event an event that is triggered by [[endPage()]].     * 事件被[endPage()]触发     */    const EVENT_END_PAGE = 'endPage';    /**     * @event ViewEvent an event that is triggered by [[renderFile()]] right before it renders a view file.     * 事件被[renderFile()]触发前呈现一个视图文件     */    const EVENT_BEFORE_RENDER = 'beforeRender';    /**     * @event ViewEvent an event that is triggered by [[renderFile()]] right after it renders a view file.     * 事件被[renderFile()]触发后呈现一个视图文件     */    const EVENT_AFTER_RENDER = 'afterRender';    /**     * @var ViewContextInterface the context under which the [[renderFile()]] method is being invoked.     * ViewContextInterface背景下 [renderFile()]方法被调用     */    public $context;    /**     * @var mixed custom parameters that are shared among view templates.     * 视图模板中共享的自定义参数     */    public $params = [];    /**     * @var array a list of available renderers indexed by their corresponding supported file extensions.     * Each renderer may be a view renderer object or the configuration for creating the renderer object.     *  一个可用的渲染索引列表。每个渲染器是一个渲染器对象或创建渲染对象配置数组     * For example, the following configuration enables both Smarty and Twig view renderers:     *     * ~~~     * [     *     'tpl' => ['class' => 'yii\smarty\ViewRenderer'],     *     'twig' => ['class' => 'yii\twig\ViewRenderer'],     * ]     * ~~~     *     * If no renderer is available for the given view file, the view file will be treated as a normal PHP     * and rendered via [[renderPhpFile()]].     */    public $renderers;    /**     * @var string the default view file extension. This will be appended to view file names if they don't have file extensions.     * 默认视图文件扩展名，文件没有扩展名的情况下自动加载     */    public $defaultExtension = 'php';    /**     * @var Theme|array|string the theme object or the configuration for creating the theme object.     * If not set, it means theming is not enabled.主题对象或创建主题对象的配置 未设置则不启用     */    public $theme;    /**     * @var array a list of named output blocks. The keys are the block names and the values     * are the corresponding block content. You can call [[beginBlock()]] and [[endBlock()]]     * to capture small fragments of a view. They can be later accessed somewhere else     * through this property.     * 一个输出块列表。键是块名称值为内容。可以调用 [beginblock()]和[endblock()]捕获视图的小片段     * 可以在其他地方通过这个属性访问。     */    public $blocks;    /**     * @var array a list of currently active fragment cache widgets. This property     * is used internally to implement the content caching feature. Do not modify it directly.     * 当前操作片段的缓存部件列表。用于内部实现内容缓存功能。不要直接修改     * @internal     */    public $cacheStack = [];    /**     * @var array a list of placeholders for embedding dynamic contents. This property     * is used internally to implement the content caching feature. Do not modify it directly.     * 嵌入动态内容占位符列表。 用于内部实现内容缓存功能。不要直接修改     * @internal     */    public $dynamicPlaceholders = [];    /**     * @var array the view files currently being rendered. There may be multiple view files being     * rendered at a moment because one view may be rendered within another.     * 正在渲染的视图文件。可能有多个视图文件被渲染，因为一个视图可以在另一个视图中呈现     */    private $_viewFiles = [];    /**     * Initializes the view component.初始化视图组件     */    public function init()    {        parent::init(); //调用父类的方法        if (is_array($this->theme)) {            if (!isset($this->theme['class'])) {                $this->theme['class'] = 'yii\base\Theme';//是数组，没有设置类名，则类名'yii\base\Theme'            }            $this->theme = Yii::createObject($this->theme);//设置了类名，调用配置创建对象        } elseif (is_string($this->theme)) {//以字符串参数的形式创建对象            $this->theme = Yii::createObject($this->theme);        }    }    /**     * Renders a view.     * 渲染一个视图     * The view to be rendered can be specified in one of the following formats:     *     * - path alias (e.g. "@app/views/site/index");     * 路径别名     * - 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.     *  绝对路径，会在[Application::viewPath|view path]下查找文件     * - absolute path within current 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 [[Controller::module|current module]].     * 模块下的绝对路径，会在[Module::viewPath|view path]下查找文件     * - relative view (e.g. "index"): the view name does not start with `@` or `/`. The corresponding view file will be     *   looked for under the [[ViewContextInterface::getViewPath()|view path]] of the view `$context`.     * 相对路径，会在[ViewContextInterface::getViewPath()|view path]下查找文件       * If `$context` is not given, it will be looked for under the directory containing the view currently     *   being rendered (i.e., this happens when rendering a view within another view).     *     * @param string $view the view name.   视图名称     * @param array $params the parameters (name-value pairs) that will be extracted and made available in the view file.     * 视图中应用参数     * @param object $context the context to be assigned to the view and can later be accessed via [[context]]     * in the view. If the context implements [[ViewContextInterface]], it may also be used to locate     * the view file corresponding to a relative view name. 对应情景     * @return string the rendering result     * @throws InvalidParamException if the view cannot be resolved or the view file does not exist.     * @see renderFile()     */    public function render($view, $params = [], $context = null)    {        $viewFile = $this->findViewFile($view, $context);//查找视图文件路径        return $this->renderFile($viewFile, $params, $context);//渲染视图文件    }    /**     * Finds the view file based on the given view name.通过视图文件名查找视图文件     * @param string $view the view name or the path alias of the view file. Please refer to [[render()]]     * on how to specify this parameter. 视图名称或路径视图文件的别名     * @param object $context the context to be assigned to the view and can later be accessed via [[context]]     * in the view. If the context implements [[ViewContextInterface]], it may also be used to locate     * the view file corresponding to a relative view name. 对应情景     * @return string the view file path. Note that the file may not exist. 文件路径     * @throws InvalidCallException if a relative view name is given while there is no active context to     * determine the corresponding view file.     */    protected function findViewFile($view, $context = null)    {        if (strncmp($view, '@', 1) === 0) {            // e.g. "@app/views/main"  判断是否是别名路径，是则获取真实路径            $file = Yii::getAlias($view);        } elseif (strncmp($view, '//', 2) === 0) {            // e.g. "//layouts/main" 以//开始，查找文件路径，拼接视图文件路径            $file = Yii::$app->getViewPath() . DIRECTORY_SEPARATOR . ltrim($view, '/');        } elseif (strncmp($view, '/', 1) === 0) {            // e.g. "/site/index"            if (Yii::$app->controller !== null) {                 //以/开始，且控制器存在，查找控制器对应的文件目录，拼接路径                $file = Yii::$app->controller->module->getViewPath() . DIRECTORY_SEPARATOR . ltrim($view, '/');            } else {                throw new InvalidCallException("Unable to locate view file for view '$view': no active controller.");            }        } elseif ($context instanceof ViewContextInterface) {            //对应情景存在 查找文件路径，拼接视图文件路径            $file = $context->getViewPath() . DIRECTORY_SEPARATOR . $view;        } elseif (($currentViewFile = $this->getViewFile()) !== false) {            //当前渲染文件存在，拼接路径            $file = dirname($currentViewFile) . DIRECTORY_SEPARATOR . $view;        } else {            throw new InvalidCallException("Unable to resolve view file for view '$view': no active view context.");        }        if (pathinfo($file, PATHINFO_EXTENSION) !== '') {            return $file;//视图文件的扩展名不为空，返回扩展名        }        $path = $file . '.' . $this->defaultExtension; //给视图文件添加扩展名        if ($this->defaultExtension !== 'php' && !is_file($path)) {            $path = $file . '.php';        }        return $path;//返回路径    }    /**     * Renders a view file.     * 渲染一个视图文件。     * If [[theme]] is enabled (not null), it will try to render the themed version of the view file as long     * as it is available.     * 如果[theme]可用，将渲染视图文件的主题版本直到[theme]不可用     * The method will call [[FileHelper::localize()]] to localize the view file.     * 调用[FileHelper::localize()]方法本地化视图文件     * If [[renderers|renderer]] is enabled (not null), the method will use it to render the view file.     * Otherwise, it will simply include the view file as a normal PHP file, capture its output and     * return it as a string.     * 如果[[renderers|renderer]]启用，该方法将用它来渲染视图文件。否则，将视图文件作为一个正常的PHP文件包含进来，获取其输出并返回一个字符串。     * @param string $viewFile the view file. This can be either an absolute file path or an alias of it.     * 视图文件。可以是绝对路径或它的别名。     * @param array $params the parameters (name-value pairs) that will be extracted and made available in the view file.     * 视图文件执行的参数     * @param object $context the context that the view should use for rendering the view. If null,     * existing [[context]] will be used.     * 用于渲染视图的上下文     * @return string the rendering result      * @throws InvalidParamException if the view file does not exist     */    public function renderFile($viewFile, $params = [], $context = null)    {        $viewFile = Yii::getAlias($viewFile);//处理输入的视图文件名        if ($this->theme !== null) {            $viewFile = $this->theme->applyTo($viewFile);//如果theme非空，应用到视图文件        }        if (is_file($viewFile)) {            $viewFile = FileHelper::localize($viewFile);//本地化视图文件        } else {            throw new InvalidParamException("The view file does not exist: $viewFile");        }        $oldContext = $this->context;        if ($context !== null) {            $this->context = $context;        }        $output = '';        $this->_viewFiles[] = $viewFile;//记录当前渲染文件        if ($this->beforeRender($viewFile, $params)) {//如果前置事件执行成功            Yii::trace("Rendering view file: $viewFile", __METHOD__);//记录trace信息            $ext = pathinfo($viewFile, PATHINFO_EXTENSION);//视图文件扩展名            if (isset($this->renderers[$ext])) {//视图文件的扩展名是否支持                if (is_array($this->renderers[$ext]) || is_string($this->renderers[$ext])) {                    $this->renderers[$ext] = Yii::createObject($this->renderers[$ext]);                }                /* @var $renderer ViewRenderer */                $renderer = $this->renderers[$ext];//赋值view渲染器对象                $output = $renderer->render($this, $viewFile, $params);//渲染视图文件            } else {//视图文件不是支持的类型，以普通php文件处理                $output = $this->renderPhpFile($viewFile, $params);            }            $this->afterRender($viewFile, $params, $output);        }        array_pop($this->_viewFiles);        $this->context = $oldContext;        return $output;    }

/**     * @return string|boolean the view file currently being rendered. False if no view file is being rendered.     * 当前正在渲染的视图文件     */    public function getViewFile()    {        return end($this->_viewFiles);    }    /**     * This method is invoked right before [[renderFile()]] renders a view file.     * The default implementation will trigger the [[EVENT_BEFORE_RENDER]] event.     * 前置事件，执行[renderFile()]时被调用，默认触发[[EVENT_BEFORE_RENDER]]事件     * If you override this method, make sure you call the parent implementation first.     * @param string $viewFile the view file to be rendered. 要渲染的视图文件。     * @param array $params the parameter array passed to the [[render()]] method.     * 参数数组传递到[render()]方法。     * @return boolean whether to continue rendering the view file. 是否继续渲染视图文件。     */    public function beforeRender($viewFile, $params)    {        $event = new ViewEvent([//实例化ViewEvent            'viewFile' => $viewFile,            'params' => $params,        ]);        $this->trigger(self::EVENT_BEFORE_RENDER, $event);//触发[EVENT_BEFORE_RENDER]事件        return $event->isValid;//判断是否继续渲染文件    }    /**     * This method is invoked right after [[renderFile()]] renders a view file.     * The default implementation will trigger the [[EVENT_AFTER_RENDER]] event.     * 后置事件，在执行[renderFile()]方法后被调用，默认触发[[EVENT_AFTER_RENDER]]事件     * If you override this method, make sure you call the parent implementation first.     * @param string $viewFile the view file being rendered.要渲染的视图文件。     * @param array $params the parameter array passed to the [[render()]] method.     * 参数数组传递到[render()]方法。     * @param string $output the rendering result of the view file. Updates to this parameter     * will be passed back and returned by [[renderFile()]].     * 返回视图渲染的结果     */    public function afterRender($viewFile, $params, &$output)    {        if ($this->hasEventHandlers(self::EVENT_AFTER_RENDER)) {//判断[EVENT_AFTER_RENDER]事件是否存在            $event = new ViewEvent([                'viewFile' => $viewFile,                'params' => $params,                'output' => $output,            ]);            //触发[EVENT_AFTER_RENDER]事件            $this->trigger(self::EVENT_AFTER_RENDER, $event);            $output = $event->output;//返回结果        }    }    /**     * Renders a view file as a PHP script.     * 返回一个视图文件当作PHP脚本     * This method treats the view file as a PHP script and includes the file.     * It extracts the given parameters and makes them available in the view file.     * The method captures the output of the included view file and returns it as a string.     * 将传入的参数转换为变量，包含并执行view文件，返回执行结果     * This method should mainly be called by view renderer or [[renderFile()]].     *     * @param string $_file_ the view file. 视图文件     * @param array $_params_ the parameters (name-value pairs) that will be extracted and made available in the view file.     * @return string the rendering result 执行结果     */    public function renderPhpFile($_file_, $_params_ = [])    {        ob_start(); //打开输出缓冲        ob_implicit_flush(false); //关闭缓冲区        extract($_params_, EXTR_OVERWRITE);// 将一个数组转换为变量使用        require($_file_);                return ob_get_clean();//得到缓冲区的内容并清除当前输出缓冲    }    /**     * Renders dynamic content returned by the given PHP statements. 渲染动态内容     * This method is mainly used together with content caching (fragment caching and page caching)     * 用来聚合缓存的内容     * when some portions of the content (called *dynamic content*) should not be cached.     * The dynamic content must be returned by some PHP statements.     * 渲染某些被PHP语句返回的动态内容     * @param string $statements the PHP statements for generating the dynamic content.生成动态内容的PHP语句。     * @return string the placeholder of the dynamic content, or the dynamic content if there is no     * active content cache currently. 动态内容占位符 如果当前没有有效的内容缓存，调用evaluateDynamicContent输出     */    public function renderDynamic($statements)    {        if (!empty($this->cacheStack)) {//动态内容的列表不为空            $n = count($this->dynamicPlaceholders);//统计动态内容条数            $placeholder = "<![CDATA[YII-DYNAMIC-$n]]>";//生成占位符            $this->addDynamicPlaceholder($placeholder, $statements);//添加动态内容占位符            return $placeholder;        } else {//没有有效缓存 执行传入的PHP语句，返回执行结果            return $this->evaluateDynamicContent($statements);        }    }    /**     * Adds a placeholder for dynamic content. 添加一个动态内容占位符     * This method is internally used. 内部使用     * @param string $placeholder the placeholder name 占位符名称     * @param string $statements the PHP statements for generating the dynamic content     * 生成动态内容的PHP语句     */    public function addDynamicPlaceholder($placeholder, $statements)    {        foreach ($this->cacheStack as $cache) {            $cache->dynamicPlaceholders[$placeholder] = $statements;//添加动态内容占位符        }        $this->dynamicPlaceholders[$placeholder] = $statements;//给当前视图添加动态内容占位符    }    /**     * Evaluates the given PHP statements. 给定的PHP语句的值     * This method is mainly used internally to implement dynamic content feature.内部使用实现动态内容功能     * @param string $statements the PHP statements to be evaluated. PHP语句进行计算     * @return mixed the return value of the PHP statements. PHP语句的值     */    public function evaluateDynamicContent($statements)    {        return eval($statements);    }    /**     * Begins recording a block.     * This method is a shortcut to beginning [[Block]]     * 数据块开始的标记，该方法是开始[Block]的快捷方式     * 数据块可以在一个地方指定视图内容在另一个地方显示，通常和布局一起使用     * @param string $id the block ID. 数据块标识     * @param boolean $renderInPlace whether to render the block content in place. 是否渲染块内容。     * Defaults to false, meaning the captured block will not be displayed.     * @return Block the Block widget instance 数据块部件实例     */    public function beginBlock($id, $renderInPlace = false)    {        return Block::begin([            'id' => $id,//数据块唯一标识            'renderInPlace' => $renderInPlace,//是否显示标识            'view' => $this,        ]);    }    /**     * Ends recording a block. 数据块结束标识     */    public function endBlock()    {        Block::end();    }    /**     * Begins the rendering of content that is to be decorated by the specified view.     * This method can be used to implement nested layout. For example, a layout can be embedded     * in another layout file specified as '@app/views/layouts/base.php' like the following:     * 开始指定的view渲染内容，用来实现嵌套布局，传入的第一个参数为布局文件的路径     * ~~~     * <?php $this->beginContent('@app/views/layouts/base.php'); ?>     * ...layout content here...     * <?php $this->endContent(); ?>     * ~~~     *     * @param string $viewFile the view file that will be used to decorate the content enclosed by this widget.     * This can be specified as either the view file path or path alias.布局文件的路径或路径别名。     * @param array $params the variables (name => value) to be extracted and made available in the decorative view.     * 可以在视图中运用的参数     * @return ContentDecorator the ContentDecorator widget instance 部件实例     * @see ContentDecorator     */    public function beginContent($viewFile, $params = [])    {        return ContentDecorator::begin([            'viewFile' => $viewFile,            'params' => $params,            'view' => $this,        ]);    }    /**     * Ends the rendering of content.结束渲染内容     */    public function endContent()    {        ContentDecorator::end();    }    /**     * Begins fragment caching. 开始片段缓存     * This method will display cached content if it is available.     * If not, it will start caching and would expect an [[endCache()]]     * call to end the cache and save the content into cache.     * 展示可用的缓存内容，否则将开始缓存内容直到出现[endCache()]方法     * A typical usage of fragment caching is as follows,     *     * ~~~     * if ($this->beginCache($id)) {     *     // ...generate content here     *     $this->endCache();     * }     * ~~~     *     * @param string $id a unique ID identifying the fragment to be cached.缓存片段的唯一标识     * @param array $properties initial property values for [[FragmentCache]]初始属性[FragmentCache]     * @return boolean whether you should generate the content for caching. 是否生成缓存的内容。     * False if the cached version is available.     */    public function beginCache($id, $properties = [])    {        $properties['id'] = $id;    //片段标识        $properties['view'] = $this;    //调用初始化属性        /* @var $cache FragmentCache */        $cache = FragmentCache::begin($properties);         if ($cache->getCachedContent() !== false) {            $this->endCache();//从缓存中读取到了缓存的内容，则渲染内容并返回 false，不再进行缓存            return false;        } else {            return true;        }    }    /**     * Ends fragment caching. 结束片段缓存     */    public function endCache()    {        FragmentCache::end();    }    /**     * Marks the beginning of a page.页面开始标记     */    public function beginPage()    {        ob_start(); //打开输出缓冲        ob_implicit_flush(false);//关闭缓冲区        $this->trigger(self::EVENT_BEGIN_PAGE);    }    /**     * Marks the ending of a page. 页面结束标记     */    public function endPage()    {        $this->trigger(self::EVENT_END_PAGE);        ob_end_flush();//关闭输出缓冲区    }