ADD B4 Actions: Save and View

README.md

@@ -439,3 +439,90 @@ just a line before `<folder>services</folder>` :
 ```
 
 ---
+
+### Adding administrator's actions (Back-end) - Save and Cancel
+In the form View, you can add action buttons like "Save" and "Cancel" to submit the form
+or cancel the editing respectively. These buttons are added to the toolbar.
+
+These buttons require compound tasks (controller and method). For example,
+
+- Save and Edit: part.apply
+- Save and Close: part.save
+- Cancel: part.cancel
+
+#### View file
+**admin/src/View/Part/HtmlView.php**
+In the View file, we create a new method to add a toolbar: `addToolbar()`. The
+toolbar hides the sidebar menu on forms, sets the title and adds action buttons.
+```php
+use Joomla\CMS\Factory;
+use Joomla\CMS\MVC\View\HtmlView as BaseHtmlView;
+use Joomla\CMS\Toolbar\Toolbar;
+use Joomla\CMS\Toolbar\ToolbarHelper;
+
+protected function addToolbar()
+{
+	Factory::getApplication()->getInput()->set('hidemainmenu', true);
+	ToolbarHelper::title('Part: Add');
+
+	ToolbarHelper::apply('part.apply');
+	ToolbarHelper::save('part.save');
+	ToolbarHelper::cancel('part.cancel', 'JTOOLBAR_CLOSE');
+}
+```
+The display() calls this method to include the toolbar.
+```php
+public function display($tpl = null) 
+{
+	$this->form = $this->get('Form');
+
+	$this->addToolbar();
+
+	parent::display($tpl);
+}
+```
+#### Controller file
+**admin/src/Controller/PartController.php***
+Now, when these action buttons are clicked, Joomla will look for apply(), save() or cancel()
+methods in the Part controller. So, create a controller clss that will extend FormController.
+These methods are already defined in the parent class.
+```php
+use Joomla\CMS\MVC\Controller\FormController;
+
+class PartController extends FormController
+{
+}
+```
+#### Model file
+
+**admin/src/model/PartModel.php**
+
+If you click on Save button, it will save the data and redirect to the editing screen. However, the data will not be present in the form. Though, we have set `$loadData` to true, we also need to create a method `loadFormData()` to get the data for the form.
+
+```php
+protected function loadFormData()
+{
+	$app  = Factory::getApplication();
+	$data = $app->getUserState('com_depot.edit.part.data', []);
+
+	if (empty($data)) {
+		$data = $this->getItem();
+	}
+
+	return $data;
+}
+```
+First, this method tries to get the data from the session. If it fails to get data from the
+session, then it gets data from the database. The `getItem()` method is defined in the
+parent class.
+
+Suppose the user has filled out the form to add a new item but has some invalid data in the
+form. In this case, the save will not be successful, so the data is not saved in the
+database. It would be very frustrating if the user hat to reenter all the fields to fix a
+single error. To handle this scenario, you save the entered data in the user's session.
+Only after the save is successful, you clear this out of the session.
+
+So, you either have data from the database, which you can get with `getItem()`, or you have
+data from the session, which you can get with `getUserSate()`.
+
+---