How do I create insert related field value from id [Laravel] - laravel

Question

First of all sorry if my title question doesn't make sense, since I don't know how to word my problem and my English not that great. Okay, so
I have my controller
Buy::create([
'master_item_id' => $request->master_item_id,
'quantity_item' => $request->quantity_item,
'price' => $request->price
]);
I have my view
<select id="master_item_id" name="master_item_id"
class="form-control #error('master_item_id') is-invalid #enderror">
<option></option>
#foreach($item as $value)
<option {{ old('master_item_id') ? 'selected' : '' }} value="{{ $value->id }}">
{{ $value->name_item }} |
Rp {{ number_format($value->price, 0, ',', '.')}}
</option>
#endforeach
</select>
How do I create insert 'price' from one form select above? I'm guessing you use where() or maybe find()? I've been flipping through website searching and couldn't find anything. Thanks!

Answer 1

Using the model called MasterItem, this could work:
Buy::create([
'master_item_id' => $request->master_item_id,
'quantity_item' => $request->quantity_item,
'price' => MasterItem::find($request->master_item_id)->price
]);
This does assume that master_item_id in your request represents the id or primary key of the MasterItem model.
If not, and you cannot use find() then this would also work:
Buy::create([
'master_item_id' => $request->master_item_id,
'quantity_item' => $request->quantity_item,
'price' => MasterItem::firstWhere('whatever_the_column_is_called', $request->master_item_id)->price
]);