yii2源码学习笔记(十九）

  1     /**
  2      * @return string|boolean the view file currently being rendered. False if no view file is being rendered.
  3      * 当前正在渲染的视图文件
  4      */
  5     public function getViewFile()
  6     {
  7         return end($this->_viewFiles);
  8     }
  9 
 10     /**
 11      * This method is invoked right before [[renderFile()]] renders a view file.
 12      * The default implementation will trigger the [[EVENT_BEFORE_RENDER]] event.
 13      * 前置事件，执行[renderFile()]时被调用，默认触发[[EVENT_BEFORE_RENDER]]事件
 14      * If you override this method, make sure you call the parent implementation first.
 15      * @param string $viewFile the view file to be rendered. 要渲染的视图文件。
 16      * @param array $params the parameter array passed to the [[render()]] method.
 17      * 参数数组传递到[render()]方法。
 18      * @return boolean whether to continue rendering the view file. 是否继续渲染视图文件。
 19      */
 20     public function beforeRender($viewFile, $params)
 21     {
 22         $event = new ViewEvent([//实例化ViewEvent
 23             'viewFile' => $viewFile,
 24             'params' => $params,
 25         ]);
 26         $this->trigger(self::EVENT_BEFORE_RENDER, $event);//触发[EVENT_BEFORE_RENDER]事件
 27 
 28         return $event->isValid;//判断是否继续渲染文件
 29     }
 30 
 31     /**
 32      * This method is invoked right after [[renderFile()]] renders a view file.
 33      * The default implementation will trigger the [[EVENT_AFTER_RENDER]] event.
 34      * 后置事件，在执行[renderFile()]方法后被调用，默认触发[[EVENT_AFTER_RENDER]]事件
 35      * If you override this method, make sure you call the parent implementation first.
 36      * @param string $viewFile the view file being rendered.要渲染的视图文件。
 37      * @param array $params the parameter array passed to the [[render()]] method.
 38      * 参数数组传递到[render()]方法。
 39      * @param string $output the rendering result of the view file. Updates to this parameter
 40      * will be passed back and returned by [[renderFile()]].
 41      * 返回视图渲染的结果
 42      */
 43     public function afterRender($viewFile, $params, &$output)
 44     {
 45         if ($this->hasEventHandlers(self::EVENT_AFTER_RENDER)) {//判断[EVENT_AFTER_RENDER]事件是否存在
 46             $event = new ViewEvent([
 47                 'viewFile' => $viewFile,
 48                 'params' => $params,
 49                 'output' => $output,
 50             ]);
 51             //触发[EVENT_AFTER_RENDER]事件
 52             $this->trigger(self::EVENT_AFTER_RENDER, $event);
 53             $output = $event->output;//返回结果
 54         }
 55     }
 56 
 57     /**
 58      * Renders a view file as a PHP script.
 59      * 返回一个视图文件当作PHP脚本
 60      * This method treats the view file as a PHP script and includes the file.
 61      * It extracts the given parameters and makes them available in the view file.
 62      * The method captures the output of the included view file and returns it as a string.
 63      * 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
 64      * This method should mainly be called by view renderer or [[renderFile()]].
 65      *
 66      * @param string $_file_ the view file. 视图文件
 67      * @param array $_params_ the parameters (name-value pairs) that will be extracted and made available in the view file.
 68      * @return string the rendering result 执行结果
 69      */
 70     public function renderPhpFile($_file_, $_params_ = [])
 71     {
 72         ob_start(); //打开输出缓冲
 73         ob_implicit_flush(false); //关闭缓冲区
 74         extract($_params_, EXTR_OVERWRITE);// 将一个数组转换为变量使用
 75         require($_file_);
 76         
 77         return ob_get_clean();//得到缓冲区的内容并清除当前输出缓冲
 78     }
 79 
 80     /**
 81      * Renders dynamic content returned by the given PHP statements. 渲染动态内容
 82      * This method is mainly used together with content caching (fragment caching and page caching)
 83      * 用来聚合缓存的内容
 84      * when some portions of the content (called *dynamic content*) should not be cached.
 85      * The dynamic content must be returned by some PHP statements.
 86      * 渲染某些被PHP语句返回的动态内容
 87      * @param string $statements the PHP statements for generating the dynamic content.生成动态内容的PHP语句。
 88      * @return string the placeholder of the dynamic content, or the dynamic content if there is no
 89      * active content cache currently. 动态内容占位符 如果当前没有有效的内容缓存，调用evaluateDynamicContent输出
 90      */
 91     public function renderDynamic($statements)
 92     {
 93         if (!empty($this->cacheStack)) {//动态内容的列表不为空
 94             $n = count($this->dynamicPlaceholders);//统计动态内容条数
 95             $placeholder = "<![CDATA[YII-DYNAMIC-$n]]>";//生成占位符
 96             $this->addDynamicPlaceholder($placeholder, $statements);//添加动态内容占位符
 97 
 98             return $placeholder;
 99         } else {//没有有效缓存 执行传入的PHP语句，返回执行结果
100             return $this->evaluateDynamicContent($statements);
101         }
102     }
103 
104     /**
105      * Adds a placeholder for dynamic content. 添加一个动态内容占位符
106      * This method is internally used. 内部使用
107      * @param string $placeholder the placeholder name 占位符名称
108      * @param string $statements the PHP statements for generating the dynamic content
109      * 生成动态内容的PHP语句
110      */
111     public function addDynamicPlaceholder($placeholder, $statements)
112     {
113         foreach ($this->cacheStack as $cache) {
114             $cache->dynamicPlaceholders[$placeholder] = $statements;//添加动态内容占位符
115         }
116         $this->dynamicPlaceholders[$placeholder] = $statements;//给当前视图添加动态内容占位符
117     }
118 
119     /**
120      * Evaluates the given PHP statements. 给定的PHP语句的值
121      * This method is mainly used internally to implement dynamic content feature.内部使用实现动态内容功能
122      * @param string $statements the PHP statements to be evaluated. PHP语句进行计算
123      * @return mixed the return value of the PHP statements. PHP语句的值
124      */
125     public function evaluateDynamicContent($statements)
126     {
127         return eval($statements);
128     }
129 
130     /**
131      * Begins recording a block.
132      * This method is a shortcut to beginning [[Block]]
133      * 数据块开始的标记，该方法是开始[Block]的快捷方式
134      * 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
135      * @param string $id the block ID. 数据块标识
136      * @param boolean $renderInPlace whether to render the block content in place. 是否渲染块内容。
137      * Defaults to false, meaning the captured block will not be displayed.
138      * @return Block the Block widget instance 数据块部件实例
139      */
140     public function beginBlock($id, $renderInPlace = false)
141     {
142         return Block::begin([
143             'id' => $id,//数据块唯一标识
144             'renderInPlace' => $renderInPlace,//是否显示标识
145             'view' => $this,
146         ]);
147     }
148 
149     /**
150      * Ends recording a block. 数据块结束标识
151      */
152     public function endBlock()
153     {
154         Block::end();
155     }
156 
157     /**
158      * Begins the rendering of content that is to be decorated by the specified view.
159      * This method can be used to implement nested layout. For example, a layout can be embedded
160      * in another layout file specified as '@app/views/layouts/base.php' like the following:
161      * 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
162      * ~~~
163      * <?php $this->beginContent('@app/views/layouts/base.php'); ?>
164      * ...layout content here...
165      * <?php $this->endContent(); ?>
166      * ~~~
167      *
168      * @param string $viewFile the view file that will be used to decorate the content enclosed by this widget.
169      * 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。
170      * @param array $params the variables (name => value) to be extracted and made available in the decorative view.
171      * 可以在视图中运用的参数
172      * @return ContentDecorator the ContentDecorator widget instance 部件实例
173      * @see ContentDecorator
174      */
175     public function beginContent($viewFile, $params = [])
176     {
177         return ContentDecorator::begin([
178             'viewFile' => $viewFile,
179             'params' => $params,
180             'view' => $this,
181         ]);
182     }
183 
184     /**
185      * Ends the rendering of content.结束渲染内容
186      */
187     public function endContent()
188     {
189         ContentDecorator::end();
190     }
191 
192     /**
193      * Begins fragment caching. 开始片段缓存
194      * This method will display cached content if it is available.
195      * If not, it will start caching and would expect an [[endCache()]]
196      * call to end the cache and save the content into cache.
197      * 展示可用的缓存内容，否则将开始缓存内容直到出现[endCache()]方法
198      * A typical usage of fragment caching is as follows,
199      *
200      * ~~~
201      * if ($this->beginCache($id)) {
202      *     // ...generate content here
203      *     $this->endCache();
204      * }
205      * ~~~
206      *
207      * @param string $id a unique ID identifying the fragment to be cached.缓存片段的唯一标识
208      * @param array $properties initial property values for [[FragmentCache]]初始属性[FragmentCache]
209      * @return boolean whether you should generate the content for caching. 是否生成缓存的内容。
210      * False if the cached version is available.
211      */
212     public function beginCache($id, $properties = [])
213     {
214         $properties['id'] = $id;    //片段标识
215         $properties['view'] = $this;    //调用初始化属性
216         /* @var $cache FragmentCache */
217         $cache = FragmentCache::begin($properties); 
218         if ($cache->getCachedContent() !== false) {
219             $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
220 
221             return false;
222         } else {
223             return true;
224         }
225     }
226 
227     /**
228      * Ends fragment caching. 结束片段缓存
229      */
230     public function endCache()
231     {
232         FragmentCache::end();
233     }
234 
235     /**
236      * Marks the beginning of a page.页面开始标记
237      */
238     public function beginPage()
239     {
240         ob_start(); //打开输出缓冲
241         ob_implicit_flush(false);//关闭缓冲区
242 
243         $this->trigger(self::EVENT_BEGIN_PAGE);
244     }
245 
246     /**
247      * Marks the ending of a page. 页面结束标记
248      */
249     public function endPage()
250     {
251         $this->trigger(self::EVENT_END_PAGE);
252         ob_end_flush();//关闭输出缓冲区
253     }