List of users in form

Question

In a component, if I want to add an user field to the form, I can easily use a field of type user, and play with it as I want.

But what can I do if I need a field that stores an array of users?

The idea is, in the backend, to be able to add one or more objects of type user to that field (let's call it, for example, collaborators), and in the frontend to be able to manipulate and show the list of users selected for that field (in the collaborators example, it could be something like Collaborators: Sophia Smith, Emma Williams, Oliver Lee.).

Edit: same question extended to an array of objects of type contact, url, etc...

Answer 1

User type field doesn't support multiple attribute. I can think of 3 options:

1. Create a custom field type with multiple support. You can use Author field as example. Just change the query to be a simple select from #__users table https://github.com/joomla/joomla-cms/blob/e6d61160eff61d749328e86c01c98fc5239a198a/libraries/src/Form/Field/AuthorField.php.

2. Use SQL field. See documentation here https://docs.joomla.org/SQL_form_field_type.

3. Use Subform field type and include User type field in it. https://docs.joomla.org/Subform_form_field_type