Implement casting to Decimal in DecimalObjectCast trait

Author: AJenbo

Diff for: src/DecimalObjectCast.php

@@ -8,9 +8,10 @@
  * "decimal" cast uses `number_format`, but we can utilize the `toFixed` method
  * provided by Decimal\Decimal to prepare the value.
  *
- * This trait does not provide a cast from string to Decimal; this should be
- * done manually using an accessor like `getPriceAttribute`, which should return
- * a new Decimal\Decimal using the precision of the column in the database.
+ * This trait extends the default behavior by allowing the precision and scale
+ * of the decimal value to be specified via the attribute's casting definition.
+ * For example, `decimal:2:8` would cast the attribute to a Decimal with 2 digits
+ * of scale and 8 digits of precision.
  */
 trait DecimalObjectCast
 {
@@ -27,7 +28,31 @@ trait DecimalObjectCast
     protected function asDecimal($value, $decimals)
     {
         assert($value instanceof Decimal);
-        
-        return $value->toFixed($decimals, $commas = false, PHP_ROUND_HALF_UP);
+        $decimals = explode(':', $decimals)[0];
+
+        return $value->toFixed($decimals, false, PHP_ROUND_HALF_UP);
+    }
+
+    /**
+     * Set a given attribute on the model.
+     *
+     * @param  string  $key
+     * @param  mixed   $value
+     *
+     * @return mixed
+     */
+    public function setAttribute($key, $value)
+    {
+        if (null !== $value) {
+            $casts = $this->getCasts();
+            if (array_key_exists($key, $casts) && $this->isDecimalCast($casts[$key])) {
+                $precision = explode(':', $this->casts[$key])[2] ?? Decimal::DEFAULT_PRECISION;
+                $this->attributes[$key] = new Decimal($value, $precision);
+
+                return $this;
+            }
+        }
+
+        return parent::setAttribute($key, $value);
     }
 }