How to implement dynamic fields on a Back End Joomla! component ?

[Stephane B]

Hi there,

I start Joomla! (3.x) component development recently and I'm facing an issue that online tutorials can't solve for me.

So far, I did very simple Back End forms following the examples shown in this tutorial : https://docs.joomla.org/J3.x:Developing_a_MVC_Component.

But now, I need to have a form where there is general and static information, plus an unknown amount of dynamic fields.

Concretely, I have an "Article" with :

- Id,
- Label,
- Description.

Here are the static fields.

And each "Article" is linked to one or many "Price". A "Price" is defined as below :

- Id,
- Label,
- Amount,
- User_Group.


Is there a way to deal with my problem ? Cause I've no idea of how to do this with the classic XML static Form definition.

Your help would be very very helpful and I thank you in advance !!

Regards,
Stéphane

[Hùng Trần]

Hi Stephane,

You can modify your form in getForm function to add new fields. I often do that like this.

class MyComponentModelMyItem extends JModelAdmin
{
    public function getForm($data = array(), $loadData = true)
    {
        // Get the form.
        $form = $this->loadForm('com_mycomponent.myitem', 'myitem', array('control' => 'jform', 'load_data' => $loadData));

        if (empty($form))
        {
            return false;
        }

        // Modify the $form object here to change field attributes or add/remove fields.

        $myFields = array(
            // Array of dynamic fields.
        );

        // Add new fields to a new fieldset.

        $xml = '<fieldset name="custom_fields">';

        foreach ($myFields as $field)
        {
            $xml .= '<field name="' . $field->name . '" type="' . $field->type . '" label="' . $field->label . '" description="' . $field->desc . '" />';
        }

        $xml .= '</fieldset>';

        // Add new fieldset to form.

        $element = new SimpleXMLElement($xml);
        $form->setField($element);

        // We can also change field attribute here.
        $form->setFieldAttribute('somefield', 'required', 'false');

        // Or remove a field.
        $form->removeField('removeme', 'somefieldset');

        $data = $this->loadFormData();

        $form->bind($data);

        return $form;
    }
}

To validate your dynamic fields you also need to do the same to validate() function, otherwise the new fields are not there to validate.

    public function validate($form, $data, $group = null)
    {

       // Add dynamic fields or modify existing fields here before validating the inputs.

        return parent::validate($form, $data, $group);
    }

I know it is really good, if anybody has a better solution please let us know.

Regards,

Hung

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[Hannes Papenberg]

If you are talking about a component that you didn't write yourself, you
might be able to modify the XML via a plugin, like the user profile
plugin does.

Hannes

[Stephane B]

Hi,

I'm talking about a component that I write myself :) 

[Stephane B]

Hi Hung,

Thanks for your answer. But this solution is still quite a bit "static" as fields are not add with JavaScript functions. It surely works, but I was wondering if there was a solution where we can add dynamic fields with javascript, when users click on a (+) button, for example.

Best regards !

Stéphane

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[Walt Sorensen]

There are two existing things that might help with what your working on.

There is the showon attribute that will help you hid/show fields based on user selection (since 3.2.4)
There is also the "repeatable" field type that will dynamically add more field when a +/- button is selected. (since 3.2)

(one caveat on repeatable fields, it's currently broken for some field types like User, Calendar, etc. Basically any field type that includes JS logic like a modal box. Currently works great for things like text boxes)

[Stephane B]

Great. I should be able to create my component with all these answers. Thanks a lot !! :)