laravel model prevent lazy loading from throwing exception when using "whenLoaded()" relationship in resource

Question

I recently started using Model::preventLazyLoading() but it actually throws an error like resource 'discount'=>$this->whenLoaded('meta',$this->meta even though the relationship is not loaded but sometimes it might be) ->discount??0), laravel version: 9.17.0

P粉920835423 · Answer

Let PHP parse your syntax here. It must load $this->meta anyway, because when PHP parses your code, it takes precedence over the whenLoaded() method.

$this->whenLoaded('meta', $this->meta->discount ?? 0)

This is why whenLoaded() can be used closure() to avoid loading relationships unless they are actually loaded. This method will first evaluate the closure after the whenLoaded() condition is met.

$this->whenLoaded('meta', function () { return $this->meta->discount ?? 0; });