Mixed relation criteria operator in Element API

Question

I have a bit complex filtering system that I try to replicate using Element API.

So far I have this which works to a degree:

Example url: training.json?reg=124&cat=99&prod=129&erp=

'criteria' => [
            'section' => 'resources',
            'search' => (craft()->request->getParam('q') ? craft()->request->getParam('q')."*" : ''),
            'relatedTo' => [
                'and', 
                craft()->request->getParam('reg'),
                (craft()->request->getParam('cat') ? craft()->request->getParam('cat') : craft()->request->getParam('reg')),
                (craft()->request->getParam('prod') ? craft()->request->getParam('prod') : craft()->request->getParam('reg')),
                (craft()->request->getParam('erp') ? craft()->request->getParam('erp') : craft()->request->getParam('reg')),
            ],
  ...

First of all, I don't know how to deal with optional parameters, I've solved this by re-using the only required parameter - reg. It works, but it's not nice, any help here would be appreciated.

The real issue though is that I need the reg parameter to be an array with all the elements in the array having OR operator.

So basically:

Example url: training.json?reg[]=124&reg=[]=123&cat=99&prod=129&erp=

(reg[0] OR reg[1]) AND cat AND prod AND erp

Is there any way I can achieve this in element API? I've tried something in the lines of the following, but with no luck.

'relatedTo' => [
     'and', 
      ['targetRegions' => ['or', 124, 99]], 
      105, 
      231,
 ],

Answer 1

Something like this should work to combine 'and' and 'or' conditions.

'relatedTo' => [
    'and',
    ['element' => [124, 99]],
    ['element' => 105],
    ['element' => 231],
],

And this is the pattern I’m usually using to build the relatedTo param dynamically. I also try to be explicit about the direction (sourceElement / targetElement) and the relation’s field.

$query = craft()->request->getQuery();

$relatedToParam = ['and'];

if ($query['reg']) {
    $relatedToParam[] = [
        'targetElement' => $query['reg'],
        'field' => 'myRegFieldHandle',
    ];
}

// repeat for all our other relatedTo conditions

$relatedToParam = count($relatedToParam) > 1 ? $relatedToParam : null,

return [
    'criteria' => [
        'section' => 'resources',
        'relatedTo' => $relatedToParam,
    ],
];