Class yii\bootstrap4\NavBar

                public function init()
{
    parent::init();
    if (!isset($this->options['class']) || empty($this->options['class'])) {
        Html::addCssClass($this->options, [
            'widget' => 'navbar',
            'toggle' => 'navbar-expand-lg',
            'navbar-light',
            'bg-light'
        ]);
    } else {
        Html::addCssClass($this->options, ['widget' => 'navbar']);
    }
    $navOptions = $this->options;
    $navTag = ArrayHelper::remove($navOptions, 'tag', 'nav');
    $brand = '';
    if (!isset($this->innerContainerOptions['class'])) {
        Html::addCssClass($this->innerContainerOptions, ['panel' => 'container']);
    }
    if (!isset($this->collapseOptions['id'])) {
        $this->collapseOptions['id'] = "{$this->options['id']}-collapse";
    }
    if ($this->brandImage !== false) {
        $this->brandLabel = Html::img($this->brandImage);
    }
    if ($this->brandLabel !== false) {
        Html::addCssClass($this->brandOptions, ['widget' => 'navbar-brand']);
        if ($this->brandUrl === null) {
            $brand = Html::tag('span', $this->brandLabel, $this->brandOptions);
        } else {
            $brand = Html::a(
                $this->brandLabel,
                $this->brandUrl === false ? Yii::$app->homeUrl : $this->brandUrl,
                $this->brandOptions
            );
        }
    }
    Html::addCssClass($this->collapseOptions, ['collapse' => 'collapse', 'widget' => 'navbar-collapse']);
    $collapseOptions = $this->collapseOptions;
    $collapseTag = ArrayHelper::remove($collapseOptions, 'tag', 'div');
    echo Html::beginTag($navTag, $navOptions) . "\n";
    if ($this->renderInnerContainer) {
        echo Html::beginTag('div', $this->innerContainerOptions) . "\n";
    }
    echo $brand . "\n";
    echo $this->renderToggleButton() . "\n";
    echo Html::beginTag($collapseTag, $collapseOptions) . "\n";
}

            

                protected function renderToggleButton()
{
    $options = $this->togglerOptions;
    Html::addCssClass($options, ['widget' => 'navbar-toggler']);
    return Html::button(
        $this->togglerContent,
        ArrayHelper::merge($options, [
            'type' => 'button',
            'data' => [
                'toggle' => 'collapse',
                'target' => '#' . $this->collapseOptions['id'],
            ],
            'aria-controls' => $this->collapseOptions['id'],
            'aria-expanded' => 'false',
            'aria-label' => $this->screenReaderToggleText,
        ])
    );
}

            

                public function run()
{
    $tag = ArrayHelper::remove($this->collapseOptions, 'tag', 'div');
    echo Html::endTag($tag) . "\n";
    if ($this->renderInnerContainer) {
        echo Html::endTag('div') . "\n";
    }
    $tag = ArrayHelper::remove($this->options, 'tag', 'nav');
    echo Html::endTag($tag);
    BootstrapPluginAsset::register($this->getView());
}

            

                public function setContainerOptions($collapseOptions)
{
    $this->collapseOptions = $collapseOptions;
}