Move calculated_value presenter method into MetricPoint getter

app/Models/MetricPoint.php

@@ -29,6 +29,15 @@ class MetricPoint extends Model implements HasPresenter
 {
     use ValidatingTrait;
 
+    /**
+     * The accessors to append to the model's array form.
+     *
+     * @var string[]
+     */
+    protected $appends = [
+        'calculated_value',
+    ];
+
     /**
      * The model's attributes.
      *
@@ -81,6 +90,16 @@ class MetricPoint extends Model implements HasPresenter
         return $this->belongsTo(Metric::class);
     }
 
+    /**
+     * Show the actual calculated value; as per (value * counter).
+     *
+     * @return int
+     */
+    public function getCalculatedValueAttribute()
+    {
+        return $this->value * $this->counter;
+    }
+
     /**
      * Round the created at value into intervals of 30 seconds.
      *

app/Presenters/MetricPointPresenter.php

@@ -19,16 +19,6 @@ class MetricPointPresenter extends BasePresenter implements Arrayable
 {
     use TimestampsTrait;
 
-    /**
-     * Show the actual calculated value; as per (value * counter).
-     *
-     * @return int
-     */
-    public function calculated_value()
-    {
-        return $this->wrappedObject->value * $this->wrappedObject->counter;
-    }
-
     /**
      * Convert the presenter instance to an array.
      *
@@ -37,9 +27,8 @@ class MetricPointPresenter extends BasePresenter implements Arrayable
     public function toArray()
     {
         return array_merge($this->wrappedObject->toArray(), [
-            'created_at'       => $this->created_at(),
-            'updated_at'       => $this->updated_at(),
-            'calculated_value' => $this->calculated_value(),
+            'created_at' => $this->created_at(),
+            'updated_at' => $this->updated_at(),
         ]);
     }
 }