How to whitelist XPC custom classes in Swift?-CodePudding

I have a pair of Swift Xcode targets that implement the XPC main app service app pattern. I figured out how to pass custom classes back and forth, either as arguments to the remote object's methods or "return values" (i.e., arguments the completion handler/reply block). This all works well.

Now I am trying to add a new wrinkle: call the completion handler with an NSArray of my custom classes from the service to return them to the main app. I understand from

it would be needed if your published interface looks like

@objc func ReadAllSnapshotsRpc(then completion: @escaping (NSArray?, Error?) -> Void)

i.e. if you would return an opaque array of unknown what, but you return explicitly typed object, so everything else is on NSSecureCoding as stated.

Update: the reason as error stated is in decoding - for decoding all class should be enumerated. Below is fixed variant:

public required init?(coder: NSCoder) {
    guard
        let partials = coder.decodeObject(of: [NSArray.self, PartialSnapshot.self], forKey: "partials") as? [PartialSnapshot]
    else {
        NSLog("ReadAllSnapshotsRpcReturnType: returning nil from init?()")
        return nil
    }
    self.partials = partials
}