update

htdocs/app/BioSpecimen.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace App;
+
+use Carbon\Carbon;
+use Illuminate\Database\Eloquent\Model;
+
+class BioSpecimen extends Model
+{
+    protected $table = 'bio_specimens';
+    protected $guarded = [];
+
+    protected $appends = ['storage_days'];
+
+    public function cabinet()
+    {
+        return $this->belongsTo(BioCabinet::class, 'cabinet_id');
+    }
+
+    public function rack()
+    {
+        return $this->belongsTo(BioRack::class, 'rack_id');
+    }
+
+    public function getStorageDaysAttribute()
+    {
+        if (!$this->stored_at) {
+            return 0;
+        }
+
+        return Carbon::parse($this->stored_at)->diffInDays(Carbon::now());
+    }
+}