BUG: passing array of Models causes an error

[pjadanowski]

Bug: Attaching an array of models causes TypeError: Illegal offset type

When passing an array of model instances to attach, it throws:

TypeError: Illegal offset type

Example:

$user->rights()->attach([Right::find(1), Right::find(2)]);

---

Cause

The issue lies in the getIdsWithAttributes method:

elseif (is_array($id)) {
    foreach ($id as $key => $attributesArray) {
        if (is_array($attributesArray)) {
            $ids[$key] = array_merge($attributes, $attributesArray);
        } else {
            $ids[$attributesArray] = $attributes;
        }
    }
} 

Here, $id is an array of models, so $attributesArray is actually a model instance of Right.
When the code runs:

$ids[$attributesArray] = $attributes;

it fails because $attributesArray is an object, not a scalar key.

---

Suggested Fix

Before using $attributesArray as an array key, you should check whether it’s a Model instance and extract its key.

Alternatively, consider adapting Laravel’s own implementation from parseIds($value):

private function parseIds($value)
{
    if ($value instanceof Model) {
        return [$value->{$this->relatedKey}];
    }

    if ($value instanceof EloquentCollection) {
        return $value->pluck($this->relatedKey)->all();
    }

    if ($value instanceof BaseCollection || is_array($value)) {
        return (new BaseCollection($value))
            ->map(fn ($item) => $item instanceof Model ? $item->{$this->relatedKey} : $item)
            ->all();
    }

    return (array) $value;
}

This approach gracefully handles model instances, arrays, or collections.
A small tweak like this inside getIdsWithAttributes() would solve the problem entirely.