Laravel comprueba si existe un modelo relacionado

I have an Eloquent model which has a related model:

public function option() {
    return $this->hasOne('RepairOption', 'repair_item_id');

public function setOptionArrayAttribute($values)

When I create the model, it does not necessarily have a related model. When I update it, I might add an option, or not.

So I need to check if the related model exists, to either update it, or create it, respectively:

$model = RepairItem::find($id);
if (Input::has('option')) {
    if (<related_model_exists>) {
        $option = new RepairOption(Input::get('option'));
    } else {

Dónde <related_model_exists> is the code I am looking for.

preguntado el 28 de mayo de 14 a las 12:05

Awesome question thank you! And great answers to the guys below. Saved me time on my project. -

11 Respuestas

In PHP 7.2+ no puedes usar count on the relation object, so there's no one-fits-all method for all relations. Use query method instead as @tremby provided below:


generic solution working on all the relation types (pre php 7.2):

if (count($model->relation))
  // exists

This will work for every relation since dynamic properties return Model or Collection. Ambos implementan ArrayAccess.

Entonces es así:

single relations: hasOne / belongsTo / morphTo / morphOne

// no related model
$model->relation; // null
count($model->relation); // 0 evaluates to false

// there is one
$model->relation; // Eloquent Model
count($model->relation); // 1 evaluates to true

to-many relations: hasMany / belongsToMany / morphMany / morphToMany / morphedByMany

// no related collection
$model->relation; // Collection with 0 items evaluates to true
count($model->relation); // 0 evaluates to false

// there are related models
$model->relation; // Collection with 1 or more items, evaluates to true as well
count($model->relation); // int > 0 that evaluates to true

Respondido 02 Jul 18, 12:07

Read whole thing. count($relation) is a general solution for all relations. It will work for Model y Collection, mientras Model no tiene ->count() método. - Jarek Tkaczyk

@CurvianVynes Not, it doesn't. Collection tiene su propio método isEmpty, pero genérico empty function returns false for an object (thus won't work for empty collection). - Jarek Tkaczyk

count($model->relation) no funcionó en morphTo when relationship had no association set yet. Foreign id and type are null and the db query built by Laravel is bogus and rises exception. I used $model->relation()->getOtherKey() como solución alternativa. - Jocelyn

@Jocelyn Yes, it's Eloquent bug. Unfortunately there are at least a few of them for polymorphic relations, so obviously you can't rely on them in any way. - Jarek Tkaczyk

It will break on PHP 7.2, returning: count(): Parameter must be an array or an object that implements Countable - CódigoGodie

A Relation object passes unknown method calls through to an Eloquent query Builder, which is set up to only select the related objects. That Builder in turn passes unknown method calls through to su subyacente query Builder.

Esto significa que puede utilizar el exists() or count() methods directly from a relation object:

$model->relation()->exists(); // bool: true if there is at least one row
$model->relation()->count(); // int: number of related rows

Note the parentheses after relation: ->relation() is a function call (getting the relation object), as opposed to ->relation which a magic property getter set up for you by Laravel (getting the related object/objects).

Usando el count method on the relation object (that is, using the parentheses) will be much faster than doing $model->relation->count() or count($model->relation) (unless the relation has already been eager-loaded) since it runs a count query rather than pulling all of the data for any related objects from the database, just to count them. Likewise, using exists doesn't need to pull model data either.

Ambos exists() y count() work on all relation types I've tried, so at least belongsTo, hasOne, hasMany y belongsToMany.

Respondido el 22 de Septiembre de 17 a las 20:09

exists is not available in lumen, not sure why. - Briankip

@briankip -- it should. You sure you're getting the relation object (by calling the method) rather than the collection (by using the magic property)? - temblar

At least in Laravel 6.x, exists doesn't work for a morphTo relationship that doesn't exist. It gets a SQL error. - Charles Wood

Tenga en cuenta que llamar exists() y count() on the relationship requires that the related model already be saved in the database. If you need to check for existence before the related model has been saved (for example, if you used setRelation), then you should use is_null or empty. - alex

@OrmanFaghihiMohaddes: the text in my answer about the query builder is just part of an explanation of how this works. You're accessing a query builder via the relation you defined on the model, so yes you absolutely still are using the relations you defined on the model. - temblar

Prefiero usar exists método:


to check if related model exists or not. It's working fine on Laravel 5.2

respondido 12 nov., 17:23

+1; count($model->relation) was returning true for me in Laravel 5.2 even though there was no item in the relation table. ->exists() does the trick. - Ben Wilson

Después Php xnumx, The accepted answer won't work for all types of relationships.

Because depending of type the relationship, Eloquent will return a Collection, Model or Null. Y en Php xnumx count(null) lanzará un error.

So, to check if the relation exist you can use:

For relationships single: For example hasOne y belongsTo

if(!is_null($model->relation)) {

For relationships multiple: For Example: hasMany y belongsToMany

if ($model->relation->isNotEmpty()) {

respondido 21 mar '18, 14:03

Worked perfectly for me! If I eager-loaded relations and executed a ->count() in a foreach loop of results, even if they were eager-loaded in the model, it would generate an SQL query for each items. Using !is_null($model->relation) is the fastest and SQL friendly way to do it. Thanks so much. - raphjutras

I use for single relationships: hasOne, belongsTo y morphs


Because if condition is null, this will be false.

For multiple relationships: hasMany, belongsToMany y morphs

if ($model->relation->isNotEmpty()) {

Respondido el 08 de Septiembre de 21 a las 07:09

Puede utilizar el relationLoaded method on the model object. This saved my bacon so hopefully it helps someone else. I was given this suggestion when I asked the same question on Laracasts.

Respondido 26 Oct 16, 16:10

As Hemerson Varela already said in Php 7.1 count(null) lanzará un error y hasOne devoluciones null if no row exists. Since you have a hasOnerelation I would use the empty método para comprobar:

$model = RepairItem::find($id);
if (!empty($temp = $request->input('option'))) {
   $option = $model->option;

      $option = $model->option()->create();

   $option->someAttribute = temp;

But this is superfluous. There is no need to check if the relation exists, to determine if you should do an update o un create call. Simply use the updateOrCreate method. This is equivalent to the above:

$model = RepairItem::find($id);
if (!empty($temp = $request->input('option'))) {  
         ->updateOrCreate(['repair_item_id' => $model->id],
                          ['option' => $temp]);

Respondido 19 Abr '19, 21:04

Not sure if this has changed in Laravel 5, but the accepted answer using count($data->$relation) didn't work for me, as the very act of accessing the relation property caused it to be loaded.

In the end, a straightforward isset($data->$relation) hizo el truco para mí.

respondido 01 mar '16, 14:03

Yo creo que es $data->relation sin $ (can't edit, because of 6 characters limit) - zanshin13

Ah el $relation would be the name of your relation, such as $data->posts or such like. Sorry if that was confusing, I wanted to make it clear that relation wasn't a concrete model property :P - Dave Stewart

This was working for a while, but it stopped working after I updated Laravel from 5.2.29 to 5.2.45. Any idea why or how to fix it? It's now causing the relational data to be loaded for some reason. - Antonio

I added an answer that has a fix for this. - Antonio

This won't work in more recent versions of Laravel. Since at least Laravel 5.8, the Model::__isset method is overloaded such that it returns true even if there is no related entity. You'll need to use !is_null to avoid the magic isset logic. They have confirmed that this is a known bug in Laravel that will be fixed in Laravel 8: - alex

I had to completely refactor my code when I updated my PHP version to 7.2+ because of bad usage of the count($x) function. This is a real pain and its also extremely scary as there are hundreds usages, in different scenarios and there is no one rules fits all..

Rules I followed to refactor everything, examples:

$x = Auth::user()->posts->find(6); (check if user has a post id=6 using ->find())

[FAILS] if(count($x)) { return 'Found'; } 
[GOOD] if($x) { return 'Found'; }

$x = Auth::user()->profile->departments; (check if profile has some departments, there can have many departments)

[FAILS] if(count($x)) { return 'Found'; }
[GOOD] if($x->count()) { return 'Found'; }

$x = Auth::user()->profile->get(); (check if user has a profile after using a ->get())

[FAILS] if(count($x)) { return 'Found'; }
[GOOD] if($x->count()) { return 'Found'; }

Hopes this can help, even 5 years after the question has been asked, this stackoverflow post has helped me a lot!

Respondido 10 Abr '20, 15:04

If you use the model class and use Eloquent ORM, then create a new method and return bool data. like

public function hasPosts(): bool
    return $this->posts()->exists();

Respondido 04 ago 21, 14:08

RelationLoaded method of Model class could be useful.

if ($this->relationLoaded('prices')) {

Respondido 13 Feb 23, 09:02

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