SceneKit, overriding the clone() method of SCNNode

Question

Created Apr ’21

Replies 3

Boosts 0

Participants 2

I've become used to inheriting SCNNode for my App and therefore adding extra variables/methods to the inherited class.

However, I've encountered a situation where I need to create a clone of the object (e.g., a copy where the geometry, materials etc. are references rather than a freshly instantiated object)
https://developer.apple.com/documentation/scenekit/scnnode/1408046-clone

However, cloning the inherited class does not, of course, clone the extra member variables in the inherited class. So I have attempted to override clone(), but i can't find an example of how this override is meant to be used in inherited classes?

Code Block class MyNode : SCNNode {
   let url: URL
   let someStruct: MyStruct
   init?(url: url, someStruct: someStruct) {
       self.url = url
       self.someStruct = someStruct
   }
    override func clone() -> Self {
         /* 
         No idea what I'm meant to do in here?
         How do I 'clone' url and someStruct members here?
         Not sure about the following code either. 
        */
        super.clone() 
        return self 
    }
}

Answered by DTS Engineer in 670203022

Hello,

In your snippet where you are overriding clone(), while at compile-time the type reported for super.clone() is SCNNode, at run-time the type will actually be your subclass "MyNode".

So, to override clone, you might do something like this:

Code Block override func clone() -> Self {         
   let clone = super.clone() as! Self // At run-time, this should be Self, so this cast is okay.
   
   clone.url = url
   clone.someStruct = someStruct
   return clone     
}

It would also be appreciated if you could file a bug report for the disagreement between the compile-time type and the run-time type using Feedback Assistant.

Boost

Answer 1

arkiruthis OP

Apr ’21

In fact, this override isn't even giving me the geometry now... I've clearly not used the base clone() correctly

Code Block language
override func clone() -> Self {
    super.clone()  
    return self  
}

0

Answer 2

DTS Engineer OP

Apple

Apr ’21

Accepted Answer

Hello,

In your snippet where you are overriding clone(), while at compile-time the type reported for super.clone() is SCNNode, at run-time the type will actually be your subclass "MyNode".

So, to override clone, you might do something like this:

Code Block override func clone() -> Self {         
   let clone = super.clone() as! Self // At run-time, this should be Self, so this cast is okay.
   
   clone.url = url
   clone.someStruct = someStruct
   return clone     
}

It would also be appreciated if you could file a bug report for the disagreement between the compile-time type and the run-time type using Feedback Assistant.

1

Answer 3

arkiruthis OP

Apr ’21

Thank you gchiste, I really appreciate the help. I've created a feedback report as requested.
FB9077227

0