plugin override Joomla MVC not working - plugins

Question

Hellow !
I must use Joomla for a website and I need to override an MVC component (com_contact) to add a field to the contact form. The problem is, I followed this tutorial :
https://docs.joomla.org/How_to_override_the_component_mvc_from_the_Joomla!_core/fr
I installed the plugin, rewrote needed files and place them where the tutorial says to place them, but it doesn't work, the plugin is not overidden.
Could someone help me with this please ?
------EDIT---------
I gave up the first tutorial and am now trying to follow this one :
https://docs.joomla.org/J3.x:Creating_a_Plugin_for_Joomla/fr
but my plugin dosen't work. Here is the code of the plugin:
/**
* Prepare form and add my field.
*
* #param JForm $form The form to be altered.
* #param mixed $data The associated data for the form.
*
* #return boolean
*
* #since <your version>
*/
function onContentPrepareForm($form, $data)
{
$app = JFactory::getApplication();
$option = $app->input->get('option');
switch ($option) {
case 'com_contact': {
if ($app->isAdmin()) {
JForm::addFormPath(__DIR__ . '/forms');
$form->loadFile('item', false);
}
return true;
}
}
return true;
}
}
?>
the contact.xml
<?xml version="1.0" encoding="UTF-8"?>
<form>
<fields name="params">
<fieldset name="params" label="PLG_CONTENT_EXAMPLE_FIELDSET_LABEL">
<field
name="contact_emaillabel2"
type="text"
label="PLG_CONTENT_EXAMPLE_CONTACT_EMAILLABEL2"
/>
<field
name="contact_email2"
type="text"
label="PLG_CONTENT_EXAMPLE_CONTACT_EMAIL2"
filter="email"
/>
</fieldset>
</fields>
</form>
install xml file :
<?xml version="1.0" encoding="utf-8"?>
<extension version="3.2" type="plugin" group="override">
<name>test</name>
<author>Laurine</author>
<creationDate>June 2016</creationDate>
<copyright>Copyright (C) Page Graphique, tous droits réservés</copyright>
<authorEmail>Laurine#page-graphique.fr</authorEmail>
<version>3.2</version>
<description>Plugin pour surcharger les composants MVC</description>
<files>
<filename>plgoverridetest.php</filename>
</files>
<config>
</config>
</extension>
arborescence :
- <Joomla>/.../plugins/override
plgoverridetest.php
install.xml
- forms
contact.xml

Answer 1

You can check this link. It will definitely help you https://docs.joomla.org/Adding_custom_fields_to_core_components_using_a_plugin.
For site usage you can use
case 'com_contact':
if ($app->isSite())
{
JForm::addFormPath(__DIR__ . '/forms');
$form->loadFile('contact', false);
}
return true;
Then you need to edit the template file. Details you can get from that link.

Answer 2

In order to override the contact form, you need to create a 'content' plugin, your plugin above is 'override' so it will not be fired by the contact component.
Also, in your code $form->loadFile('item', false); is wrong because the xml file you're trying to load is 'contact.xml' so your code should be $form->loadFile('contact', false);.
I've just completed the development of a plugin that adds many fields such as phone, website, company, file upload, newsletter and includes switching off the default fields if need be. It also sends the information to HubSpot if you use their CRM.
Now the thing is in order to use these extra fields you need to create a 'contact' plugin that's fired when the form is submitted and triggered with the plugin trigger 'onSubmitContact($data)', I've created a 'custom reply' plugin for this purpose.
You need to remember when using a custom reply plugin you must select the 'Custom Reply' option on the contact options in the admin component.
Also, the plugins I've created work on a per form basis rather than having the same fields on multiple forms you can modify each form independently.