When I run my application and use .runModal() on an instance of NSSavePanel I get the following warning.

"WARNING: <NSSavePanel: 0x10065b750> found it necessary to prepare implicitly; please prepare panels using NSSavePanel rather than NSApplication or NSWindow."

I'm assuming this has something to do with Sandboxing and PowerBox, but I've not been able to figure out the correct way they'd like me to call it.

if anyone has any insight it'd be greatly appreciated.

Here is the suspect code.

    @IBAction func saveDocument(_ sender: Any) {
        // Save Commands here.

        let savePanel = NSSavePanel()
        savePanel.title = "Save Example..."
        savePanel.prompt = "Save to file"
        savePanel.nameFieldLabel = "Pick a name"
        savePanel.nameFieldStringValue = "example.png"
//        savePanel.isExtensionHidden = false
        savePanel.canSelectHiddenExtension = true
        savePanel.allowedFileTypes = ["png"]

        let result = savePanel.runModal()

        switch result {
        case .OK:
            guard let saveURL = savePanel.url else { return }
            if let image = exampleOutputImageView.image {
                image.writePNG(to: saveURL)
            } else {
                let alert = NSAlert()
                alert.messageText = "Error"
                alert.informativeText = "Failed to save image."
                alert.alertStyle = .informational
                alert.addButton(withTitle: "OK")
                alert.runModal()
            }
        case .cancel:
            print("User Cancelled")
        default:
            print("Panel shouldn't be anything other than OK or Cancel")
        }
    }

I am having the same problem when ever I have to replace a file.
Would love some insite myself.