Element API return a type of Category

Question

I'm just wondering when it comes to Element API is there a way of returning a type of Category.

I'm returning all the other information fine.

'fees.json' => [
    'elementType' => 'Entry',
        'criteria' => [
            'title' => craft()->request->getQuery('title'),
            'section' => 'fees',
        ],
        'transformer' => function(EntryModel $entry) {
            foreach ($entry->fee as $block) {
                $matrixSections[] = [
                    'first' => $block->firstInstallment,
                    'second' => $block->secondInstallment,
                    'full' => $block->full,
                    'grant' => $block->feeCategory
                ];
            }
        return [
            'title' => $entry->title,
            'menu' => [
                'sections' => $matrixSections
            ]
        ];
    }
]

Answer 1

The Element API plugin returns JSON, so you'll need to be specific about what you want to return for your categories – i.e. you can't return a CategoryModel (or an array of CategoryModels) in full directly from a Categories field.

The easiest option is to use array_map() like this:

'first' => $block->firstInstallment,
'second' => $block->secondInstallment,
'full' => $block->full,
'grant' => array_map(function (CategoryModel $category) {
    return [
        'id' => $category->id,
        'title' => $category->title,
    ];
}, $block->categoriesField->find()),

Of course, if your individual category has a lot of fields, you can always create an external function in your elementapi.php file and use that for the array_map call, instead of inlining the function (the external function needs to live above the return ['endpoints']... part):

function getCategoryData(CategoryModel $category)
{
    return [
        'id' => $category->id,
        'title' => $category->title,
        ...
    ];
}

...

'grant' => array_map('getCategoryData', $block->categoriesField->find()),

Also, there's the $category->getAttributes() method which can be handy if you want to return all stock attributes (i.e. id, dateUpdated etc – pretty much everything sans the title, for some reason):

function getCategoryData(CategoryModel $category)
{
    return array_merge($category->getAttributes(), [
        'title' => $category->title,
        'someCustomField' => $category->someCustomField,
    ];
}

Answer 2

I'm sure the answer from Mats also works but I thought the cleaner way would be the following.

'fees.json' => [
        'elementType' => 'Entry',
            'criteria' => [
                'title' => craft()->request->getQuery('title'),
                'section' => 'fees',
            ],
            'transformer' => function(EntryModel $entry) {
            $matrixSections = [];
            foreach ($entry->fee as $block) {
            $items = [];

            foreach ($block->grantType as $itemEntry) {
                $items[] = [
                'title' => $itemEntry->title,
                ];
            }
            $matrixSections[] = [
                'first' => $block->firstInstallment,
                'second' => $block->secondInstallment,
                'full' => $block->full,

                'items' => $items,
            ];
            }
            return [
                'title' => $entry->title,
                'menu' => [
                    'sections' => $matrixSections,
                ]
            ];
        }
]