Joomla 4.x Tutorial - Extension Development - Extend the Menu Item with a Variable

Sometimes you need to customize the frontend output for a menu item. For this you need a variable. In this part of the tutorial we will add a text variable to the menu item and use it for the display in the frontend.

For impatient people: View the changed program code in the Diff View^{github.com/astridx/boilerplate/compare/t4...t5} and copy these changes into your development version.

Step by step

New files

No new file is added in this chapter. We only change files.

Modified files

components/com_foos/ src/Model/FooModel.php

In the model, change the method in which text is calculated for output. Delete the following entry:

components/com_foos/ src/Model/FooModel.php

...
		if (!isset($this->message))
		{
			$this->message = 'Hello Foo!';
		}
...

Add the following lines in its place:

...
		$app = Factory::getApplication();
		$this->message = $app->input->get('show_text', "Hi");
...

You can do without the check if (!isset($this->message)) in the new variant because the statement get('show_text', "Hi"); catches the error that occurs when the parameter show_text is not set. Whenever the value show_text is not set, the second parameter "Hi" is used as default.

The complete file looks like this in the Diff view:

components/com_foos/ src/Model/FooModel.php

\defined('_JEXEC') or die;

use Joomla\CMS\Factory;
 use Joomla\CMS\MVC\Model\BaseDatabaseModel;

 /**

 	 */
 	public function getMsg()
 	{
		if (!isset($this->message))
		{
			$this->message = 'Hello Foo!';
		}
		$app = Factory::getApplication();
		$this->message = $app->input->get('show_text', "Hi");

 		return $this->message;
 	}

So far, so good. We are still missing the possibility to configure the value for show_text at the menu item in the backend. We implement this next in the file default.xml.

components/com_foos/ tmpl/foo/default.xml

In your extension you offer the possibility to save a value at the menu item by extending the XML file with an input element. The following code shows you how to add a text input field.

components/com_foos/ tmpl/foo/default.xml

 			<![CDATA[COM_FOOS_FOO_VIEW_DEFAULT_DESC]]>
 		</message>
 	</layout>
	<!-- Add fields to the request variables for the layout. -->
	<fields name="request">
		<fieldset name="request">
			<field
				name="show_text"
				type="text"
				label="COM_FOOS_FIELD_TEXT_SHOW_LABEL"
				default="Hi"
			/>
		</fieldset>
	</fields>
 </metadata>

The XML entry

<field
	name="show_text"
	type="text"
	label="COM_FOOS_FIELD_TEXT_SHOW_LABEL"
	default="Hi"
/>

turns Joomla into the following HTML code for the output in the backend form:

<div class="control-label">
  <label id="jform_request_show_text-lbl" for="jform_request_show_text">
    COM_FOOS_FIELD_TEXT_SHOW_LABEL</label
  >
</div>
<div class="controls has-success">
  <input
    type="text"
    name="jform[request][show_text]"
    id="jform_request_show_text"
    value="Hi"
    class="form-control valid form-control-success"
    aria-invalid="false"
  />
</div>

With type="text" we use one of the simplest form fields, that is the one of type text. Various types of form fields are built into Joomla. The Joomla documentation lists these standard types. Take a look at the table on the website docs.joomla.org/Form_field/en. Often you can implement a special requirement with a special field.

Test your Joomla component

1. install your component in Joomla version 4 to test it: Copy the files in the components folder to the components folder of your Joomla 4 installation. A new installation is not necessary. Continue using the ones from the previous part.
2. switch to the Menu Manager and open a created menu item or create a new one. Here you will now see a text field where you can insert any text.

3. now switch to the frontend view. Make sure that the text you entered for the menu item is displayed in the correct variant in the frontend.

I'm sure you can think of funnier or more useful examples. But the sense and function of the variables will be clear.

4. Create multiple menu items, each containing different text. Don't just output the text on the frontend, style the output using conditional statements^{developer.mozilla.org/en/docs/web/javascript/reference/statements/if...else}. A popular use case is to change the design of the output using variables. For example, you use the variable to query whether the content is to be output in a list or in a table.