Added Nav widget closes #367

framework/yii/bootstrap/Nav.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\bootstrap;
+
+use yii\base\InvalidConfigException;
+use yii\helpers\base\ArrayHelper;
+use yii\helpers\Html;
+
+/**
+ * Nav renders a nav HTML component.
+ *
+ * For example:
+ *
+ * ```php
+ * echo Nav::widget(array(
+ *     'items' => array(
+ *         array(
+ *             'label' => 'Home',
+ *             'url' => '/',
+ *             'options' => array(...),
+ *             'active' => true,
+ *         ),
+ *         array(
+ *             'label' => 'Dropdown',
+ *             'dropdown' => array(
+ *                  array(
+ *                      'label' => 'DropdownA',
+ *                      'url' => '#',
+ *                  ),
+ *                  array(
+ *                      'label' => 'DropdownB',
+ *                      'url' => '#',
+ *                  ),
+ *             ),
+ *         ),
+ *     ),
+ * ));
+ * ```
+ *
+ * @see http://twitter.github.io/bootstrap/components.html#nav
+ * @author Antonio Ramirez <amigo.cobos@gmail.com>
+ * @since 2.0
+ */
+class Nav extends Widget
+{
+	/**
+	 * @var array list of items in the nav widget. Each array element represents a single
+	 * menu item with the following structure:
+	 *
+	 * ```php
+	 * array(
+	 *     // required, the menu item label.
+	 *     'label' => 'Nav item label',
+	 *     // optional, the URL of the menu item. Defaults to "#"
+	 *     'url'=> '#',
+	 *     // optional, the HTML options of the URL.
+	 *     'urlOptions' => array(...),
+	 *     // optional the HTML attributes of the item container (LI).
+	 *     'options' => array(...),
+	 *     // optional, an array of [[Dropdown]] widget items so to display a dropdown menu on the tab header.
+	 *     // important: there is an issue with sub-dropdown menus, and as of 3.0, bootstrap won't support sub-dropdown
+	 *     // @see https://github.com/twitter/bootstrap/issues/5050#issuecomment-11741727
+	 *     'dropdown'=> array(...)
+	 * )
+	 * ```
+	 *
+	 * Optionally, you can also use a plain string instead of an array element.
+	 */
+	public $items = array();
+
+
+	/**
+	 * Initializes the widget.
+	 */
+	public function init()
+	{
+		$this->addCssClass($this->options, 'nav');
+	}
+
+	/**
+	 * Renders the widget.
+	 */
+	public function run()
+	{
+		echo $this->renderItems();
+	}
+
+	/**
+	 * Renders widget items.
+	 */
+	public function renderItems()
+	{
+		$items = array();
+		foreach ($this->items as $item) {
+			$items[] = $this->renderItem($item);
+		}
+
+		return Html::tag('ul', implode("\n", $items), $this->options);
+	}
+
+	/**
+	 * Renders a widget's item.
+	 * @param mixed $item the item to render.
+	 * @return string the rendering result.
+	 * @throws InvalidConfigException
+	 */
+	public function renderItem($item)
+	{
+		if (is_string($item)) {
+			return $item;
+		}
+		if (!isset($item['label'])) {
+			throw new InvalidConfigException("The 'label' option is required.");
+		}
+		$label = $item['label'];
+		$url = ArrayHelper::getValue($item, 'url', '#');
+		$options = ArrayHelper::getValue($item, 'options', array());
+		$urlOptions = ArrayHelper::getValue($item, 'urlOptions', array());
+		$dropdown = null;
+
+		// does it has a dropdown widget?
+		if (isset($item['dropdown'])) {
+			$urlOptions['data-toggle'] = 'dropdown';
+			$this->addCssClass($options, 'dropdown');
+			$this->addCssClass($urlOptions, 'dropdown-toggle');
+			$label .= ' ' . Html::tag('b', '', array('class' => 'caret'));
+			$dropdown = Dropdown::widget(array('items' => $item['dropdown'], 'clientOptions' => false));
+		}
+
+		return Html::tag('li', Html::a($label, $url, $urlOptions) . $dropdown, $options);
+	}
+}
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