instanceof is your best ally in Polymorphic Relationships in Laravel

Here I want to show you a possible use of instanceof in polymorphic relationships in Laravel

Remember that with instanceof what we are indicating is to know if the object we are passing is an instance of a particular class in this case books can be post image depending on the theme you are working with.

So here I will first explain the relationship here I have the book one which is the main one as you can see:

class Book extends Model
{
   ***

   public function files()
   {
       return $this->morphMany(File::class, 'fileable');
   }
}

And a book can have c to n files as you can see so it is a one to many type between books and files and files can be books can be images can be anything:

class File extends Model
{
   ***

   protected $fillable = ['file', 'type', 'fileable_type', 'fileable_id'];

   public function fileable(): MorphTo
   {
       return $this->morphTo();
   }
}

Here you can see a little bit of what the definition of a file is based on polymorphic relationships in Laravel:

public function fileable(): MorphTo
   {
       return $this->morphTo();
   }

This is important because if we do not receive a file directly, a file that is generic, so to speak, that is to say, at a given moment it is a book, but depending on the record it could be, I don't know, a video, it could be an image, it could be anything. What I mean is that just by receiving a file here I cannot assume that it is a book. I think that is quite clear and I do not want to receive the book here for the reasons mentioned before, because it is supposed to be included here:

if ($file->fileable instanceof Book) {
  // TODO
}

What we are downloading according to the theme of this controller that says Book controller we can already assume that this has to be a book, which is what I want to work on here but obviously we have to implement the application so that it is error-free therefore files in the future again can be videos, can be images, can be anything and therefore I want to avoid any problem in which an attacking user or by mistake of mine or whatever can receive here another type of file that is not a book and I remember again that it is a polymorphic relationship of type here in Book we have the files So what I want to get to is that when I go to process this file I want to be completely sure that it is a book so that then the subsequent process does not give me any problem that in this case the subsequent process as we show in the previous code.

16-10-2024 - Andrés Cruz

En español

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