yii2 Widgets 下的widget() begin() end() 方法

2020-08 Yii2.0

widget()

    /**
     * Creates a widget instance and runs it.
     * The widget rendering result is returned by this method.
     * @param array $config name-value pairs that will be used to initialize the object properties
     * @return string the rendering result of the widget.
     * @throws \Exception
     */
    public static function widget($config = [])
    {
        ob_start();
        ob_implicit_flush(false);
        try {
            /* @var $widget Widget */
            $config['class'] = get_called_class();
            $widget = Yii::createObject($config);
            $out = '';
            if ($widget->beforeRun()) {
                $result = $widget->run();
                $out = $widget->afterRun($result);
            }
        } catch (\Exception $e) {
            // close the output buffer opened above if it has not been closed already
            if (ob_get_level() > 0) {
                ob_end_clean();
            }
            throw $e;
        }
        return ob_get_clean() . $out;
    }

begin()

    /**
     * Begins a widget.
     * 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.
     * As some widgets may use output buffering, the [[end()]] call should be made in the same view
     * to avoid breaking the nesting of output buffers.
     * @param array $config name-value pairs that will be used to initialize the object properties
     * @return static the newly created widget instance
     * @see end()
     */
    public static function begin($config = [])
    {
        $config['class'] = get_called_class();
        /* @var $widget Widget */
        $widget = Yii::createObject($config);
        self::$stack[] = $widget;
        return $widget;
    }

end()

    /**
     * Ends a widget.
     * Note that the rendering result of the widget is directly echoed out.
     * @return static the widget instance that is ended.
     * @throws InvalidCallException if [[begin()]] and [[end()]] calls are not properly nested
     * @see begin()
     */
    public static function end()
    {
        if (!empty(self::$stack)) {
            $widget = array_pop(self::$stack);
            if (get_class($widget) === get_called_class()) {
                /* @var $widget Widget */
                if ($widget->beforeRun()) {
                    $result = $widget->run();
                    $result = $widget->afterRun($result);
                    echo $result;
                }
                return $widget;
            }
            throw new InvalidCallException('Expecting end() of ' . get_class($widget) . ', found ' . get_called_class());
        }
        throw new InvalidCallException('Unexpected ' . get_called_class() . '::end() call. A matching begin() is not found.');
    }

参考资料:
Widgets
源码文件
ob_implicit_flush