Element API unable to get all() of matrix field

Question

I'm getting matrix block content from an entry type which works fine for the most part. It's probably clearer to just paste in the code:

Current element api code:

$relationsData = [];    
if($entry->relatedContent){
    $index = -1;
    foreach ($entry->relatedContent->all() as $block) {
        switch ($block->type->handle) {
            case 'relateContent':
                $index++;
                $relatedFeaturedEntries =  $block->featured->first();
                $relatedSubEntries =  $block->related->first();
                $relationsData[$index] = [
                    'title' => $relatedFeaturedEntries->title,
                    'url' => $relatedFeaturedEntries->url
                ];
                $relationsData[$index]['subItems'] = [];
                $relationsData[$index]['subItems'][] = [
                    'title' => $relatedSubEntries->title,
                    'url' => $relatedSubEntries->url
                ];
            break;
        }
    }
}

Which outputs:

      "relations": [
        {
          "title": "Testing workflow",
          "url": "http://localhost/blah",
          "subItems": [
            {
              "title": "Help & Guidance",
              "url": "http://localhost/help-guidance"
            }
          ]
        },
        {
          "title": "Taking part in the blah",
          "url": "http://localhost/blah",
          "subItems": [
            {
              "title": "blah timeline",
              "url": "http://localhost/blah"
            }
          ]
        },
        {
          "title": "Testing workflow",
          "url": "http://localhost/blah",
          "subItems": [
            {
              "title": "Completing on paper",
              "url": "http://localhost/blah"
            }
          ]
        }
      ],

There should be more subItems in each subItems array but I am only getting the first because I'm fetching them using $relatedSubEntries = $block->related->first(); But nothing else works and just errors i.e. all() or removing first()

Answer 1

Figured it out in the end. As an array is being returned I just needed a for loop to get inside it.

Solution...

                    if($entry->relatedContent){
                        $index = -1;
                        foreach ($entry->relatedContent->all() as $block) {
                            switch ($block->type->handle) {
                                case 'relateContent':
                                    $index++;
                                    $relatedFeaturedEntries =  $block->featured->first();
                                    $relationsData[$index] = [
                                        'title' => $relatedFeaturedEntries->title,
                                        'url' => $relatedFeaturedEntries->url
                                    ];

                                    $relationsData[$index]['subItems'] = [];
                                    $relatedSubEntries =  $block->related->all();
                                    foreach ($relatedSubEntries as $relatedSubEntry) {
                                        $relationsData[$index]['subItems'][] = [
                                            'title' => $relatedSubEntry->title,
                                            'url' => $relatedSubEntry->url
                                        ];
                                    }
                                break;
                            }
                        }
                    }