How to save Asset field of an Entry programmatically in Craft 3

Question

Using this answer on how to save data on Craft 3, I want to save also an asset field, but I cannot find out how.

It works for a Category field using the ids of the categories but not with ids of Assets.

Here is the code:

use craft\elements\Entry;
use craft\elements\MatrixBlock;

// Figure out the section & entry type
$section = Craft::$app->sections->getSectionByHandle('news');
$entryTypes = $section->getEntryTypes();
$entryType = reset($entryTypes);

// Create an entry
$entry = new Entry([
    'sectionId' => $section->id,
    'typeId' => $entryType->id,
    'fieldLayoutId' => $entryType->fieldLayoutId,
    'authorId' => 1,
    'title' => 'My Entry',
    'slug' => 'my-entry',
    'postDate' => new DateTime(),
]);

// search categories and retrieve therir ids
$categorySlugs = ['cat1','cat2','cat3'];
$craftCategoryIds = [];
foreach ($categorySlugs as $cs) {
    $craftCategoryIds[] = Category::find()->wpSlug($cs)->one()->id;
}

// get a an asset to be used as a featureImage
$featureImageId = Asset::find()->myField('123')->one()->id;

// Set the custom field values (including Matrix)
$fieldValues = [
    'summary' => 'Some "summary" custom field value...',
    'categories' => $craftCategoryIds, // <-- this works, categories are assigned
    'featuredImage' => $featureImageId, // <-- doesn't work, featured image is not set
    'matrixField' => [
        'new1' => [
            'type' => 'blockTypeHandle',
            'fields' => [
                    // the block's custom field values...
            ],
        ],
        'new2' => [
            'type' => 'blockTypeHandle',
            'fields' => [
                    // the block's custom field values...
            ],
        ],
    ],
]);

$entry->setFieldValues($fieldValues)

// Save the entry
Craft::$app->elements->saveElement($entry);

Answer 1

That's because you have to insert an array of ids rather than a single id

$craftCategoryIds

is an array.

$featureImageId

is an integer. Even if you have just a single element you need to insert an array

'featuredImage' => [$featureImageId]

will work