how to load relation from relation in laravel api resource

Question

I am playing for the first time with API Resource in laravel 12.

I have this situation:

The product has many Skus:

public function skus(): HasMany
{
   return $this->hasMany(Sku::class);
}

The skus has many images:

public function images(): HasMany
{
   return $this->hasMany(SkuImage::class)->orderBy('sort');
}

So from the product controller I use:

Product::with(['skus.images'])....

to receive the skus and the images.

In ProductResource:

...
'skus' => $this->whenLoaded('skus', function () {
    return $this->skus->map(function ($sku) {
        return [
           'id' => $sku->id,
           ...
           // the problem is here -> Call to undefined method App\\Models\\Sku::whenLoaded()
           'images' => $sku->whenLoaded('images', function ($sku) {
               return $sku->images->map(function ($image) {
                   return [
                       'id' => $image->id,
                       'filename' => $image->filename,
                       'size' => $image->size,
                   ];
               });
           }),
        ];
    });
}),
...

I want to load the images only when the images relation is loaded from skus with(['skus.images']), else show only the sku data with(['skus']) when not loading the images.

How can I do that?

did you install the spatie/query-builder package? i guess this method is of that package — sandip bharadva
– sandip bharadva, Commented Jun 27 at 10:36
look into the package salamwaddah/laravel-relation-parser it allows you to conditionally load relations based on the request. — Salam
– Salam, Commented Jul 1 at 12:37

parth · Accepted Answer · 2025-06-28 03:35:41Z

As error suggest whenLoaded is undefined method. whenLoaded only works on models on which resource is called on.

Solution 1

You can use relationLoaded for images.

use Illuminate\Http\Resources\MissingValue;

...
'skus' => $this->whenLoaded('skus', function () {
    return $this->skus->map(function ($sku) {
        return [
            'id' => $sku->id,
            'images' => $sku->relationLoaded('images') ?
                $sku->images->map(function ($image) {
                    return [
                        'id' => $image->id,
                        'filename' => $image->filename,
                        'size' => $image->size,
                    ];
                }) : app(MissingValue::class),
        ];
    });
}),
...

Solution 2

You can define resources for model separately.

In ProductResource:

'skus' => $this->whenLoaded('skus', $this->skus->toResource()),

In SkuResource:

'id' => $this->id,
'images' => $this->whenLoaded('images', $this->images->toResource()),

In ImageResource:

'id' => $this->id,
'filename' => $this->filename,
'size' => $this->size,

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