How can I create a custom list formfield from json

Question

I need to create a custom formfield like so:

https://docs.joomla.org/Creating_a_custom_form_field_type

But the data I want to populate the list with is in a json file. So I can't really do a PHP for each, or if I do, I need to somehow do a JS for each at the same time.

Any advice you can provide to steer me, even to resources would be appreciated.

Answer 1

Here was the final answer which was placed in mod_modulename/models/fields/stackexchangesites.php

<?php
// Check to ensure this file is included in Joomla!
defined('_JEXEC') or die('Restricted access');

// load the list class
JFormHelper::loadFieldClass('list');

// The class name must always be the same as the filename (in camel case).  
// Extend the list class
class JFormFieldStackexchangesites extends JFormFieldList
{

    //The field class must know its own type through the variable $type.
    protected $type = 'Stackexchangesites';

    // declare the function to get options
    public function getOptions()
    {

        // assign JSON to a variable
        $json = '{"items":[{"aliases":["http://www.stackoverflow.com","http://facebook.stackoverflow.com"],.....~';

        // decode the JSON, and set it as an associative array
        $sites = json_decode($json, true);

        // set the value of i so we can iterate over it
        $i = 0;

        // run a foreach on our JSON to get the values for our options
        foreach($sites['items'] as $site)
        {
            // find the api_site_parameter
            $stackExchangesSitesOptions[] = $site['api_site_parameter'];

            // iterate our i
            $i++;
        }

        // Merge any additional options in the XML definition.
        $options = array_merge(parent::getOptions(), $stackExchangesSitesOptions);
        return $options;
    }
}

Finally, in my XML

..~
    <config>
        <fields name="params">
            // add field path so it knows where to look
            <fieldset name="basic" addfieldpath="/modules/mod_kou_stack_exchange/models/fields">
                ..~
                // include your field
                <field
                        name="stackexchangesites"
                        type="stackexchangesites"
                        label="Stackexchange Sites"
                        description="JFIELD_TITLE_DESC"
                        showon="live_or_beta_stackexchange_sites:live"
                />
                ..~

All the field does is create a dropdown with a list of all the stackexchange sites. The final output of the module loads questions from a stack exchange site based on the user.