如何最好地实现一对多关系 Laravel

Question

I am working with Laravel for the backend. I am wanting to save a model, let's say it is Shirts to my database. A shirt can have many different sizes, so i want to be able to save a record of shirts like so into my database:

{
   "name": "A good shirt",
   "descripton": "this shirt is very good",
   "price": "$100",
   "sizes": ["XL","L","M","S"]  <--------- what I want
}  

My question is, how can I save implement this in my backend? How can I save an array of different sizes to my model AND make sure that when this record is saved, it meets one of the available shirt sizes? For example, I want to make sure that a shirt can only have sizes from small to extra large.

I thought about creating a new model called Shirt_Sizes and having the records be the available shirt sizes, then setting a foreign key in my Shirt Model to this. But I am having a difficult time figuring out how to save many shirt sizes to the Shirt model.

I am open to other suggestions that work outside of this.

Thank you!

Answer 1

If a shirt has many sizes and the sizes can belong to many shirts then you must Define a many to many relationship, You can make a separate table sizes for shirts sizes and then create a second table shirt_size that contains shirt_id & size_id link them with a foreign key to your shirts & sizes table.

Then you will define the appropriate relationships between the two models

Size Model

class Size extends Model
   {
   // Get the shirts for this size.
   public function shirts()
   {
       return $this->belongsToMany(Shirt::class, 'shirt_size', 'size_id', 'shirt_id');
   }
} 

Shirt Model

class Shirt extends Model
{
   // Get the size for the shirt.
   public function sizes()
   {
        return $this->belongsToMany(Size::class, 'shirt_size', 'shirt_id', 'size_id');
   }
}

Then when you need to store a new shirt with the sizes, it depends on what you send with your request:

1. Sending an array of sizes ids :

   Then you will need to verify the ids using validate :

 $validatedData = $request->validate([
     'sizes.*.size_id' => 'required|integer|exists:sizes,id',
 ]);

2. Sending an array of sizes names :

   Then you will need to verify the names using validate :

 $validatedData = $request->validate([
     'sizes.*.size_name' => 'required|string|exists:sizes,name',
 ]);

Then after creating a shirt record you can use an the attach() method to save multiple sizes for a shirt:

foreach ($validatedData['sizes'] as $size){
   $shirt->sizes()->attach($size['size_id']);
}

Or

foreach ($validatedData['sizes'] as $size){
   $size_id  = Size::where('size_name',$size['name'])->get('id'));
   $shirt->sizes()->attach($size_id);
}

Answer 2

The scenario you have is many-to-many relationships, that is, a shirt can have many sizes and one size can have many shirts, so I recommend creating two table tables as specified by the Laravel documentation. https://laravel.com/docs/7.x/eloquent-relationships#many-to-many

 shirt id - integer name - string description - string price - integer sizes id - integer name - string sizes_shirts shirt_id - integer size_id - integer

Your models look like:

 <?php namespace App; use Illuminate\Database\Eloquent\Model; class Shirt extends Model { /** * The sizes that belong to the shirt. */ public function sizes() { return $this->belongsToMany('App\Size'); } }

How to save sizes for a shirt:

$sizes_ids = [1, 2, 3];
$shirt->sizes()->sync($sizes_ids);

How to get sizes for a shirt:

$sizes_of_shirt = $shirt->sizes;