How to Check if a Related Model Exists in Laravel?

Checking Existence of Related Models in Laravel

In Laravel, Eloquent models represent database entities and provide convenient methods for managing relationships between those entities. However, when working with relationships, it may be necessary to check if a related model exists before performing further operations.

Consider the following code:

<code class="php">public function option() {
    return $this->hasOne('RepairOption', 'repair_item_id');
}

public function setOptionArrayAttribute($values)
{
    $this->option->update($values);
}</code>

In this scenario, we have a model that has a one-to-one relationship with another model. When creating or updating this model, we need to determine if the related model exists to decide whether to update or create it.

Solution 1 (Laravel 7.2 ):

In Laravel 7.2 and higher, you can use the exists() method on the relation object to check if the related model exists:

<code class="php">$model = RepairItem::find($id);
if (Input::has('option')) {
    if ($model->option()->exists()) {
        // Option exists, update it
    } else {
        // Option does not exist, create it
    }
}</code>

Solution 2 (Pre-Laravel 7.2):

In Laravel versions prior to 7.2, you can use the count() method on the relation object to check if the related model exists:

<code class="php">if (count($model->option)) {
    // Option exists
} else {
    // Option does not exist
}</code>

Note: This method only works if the relation is a single-value relation (e.g., hasOne, belongsTo). For many-to-many or other collection-based relationships, you can use methods like count() or isNotEmpty() on the relation's collection to check if it contains any related models.

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