import SpriteKit

class MOptionWhistlesVsZombiesWhistle
{
    private weak var textures:MOptionWhistlesVsZombiesWhistleTextures!
    
    required init(textures:MOptionWhistlesVsZombiesWhistleTextures)
    {
        self.textures = textures
    }
}

import Foundation

class MOptionWhistlesVsZombiesWhistle
{
    
}

--- 
+++ 
@@ -1,6 +1,11 @@
-import Foundation
+import SpriteKit
 
 class MOptionWhistlesVsZombiesWhistle
 {
+    private weak var textures:MOptionWhistlesVsZombiesWhistleTextures!
     
+    required init(textures:MOptionWhistlesVsZombiesWhistleTextures)
+    {
+        self.textures = textures
+    }
 }
Create required init for whistle model

Whistle model is going to be instantiated with
a Type and it needs a required init to be called.
This required init asks for whistle textures model.
