Manipulating files outside of sandbox
First, we need to ask for the user's permission to access the folder, but for that, we need an NSSavePanel:
let op = NSSavePanel()
op.message = "Descriptive message here"
op.canCreateDirectories = false
op.canChooseDirectories = false
op.showsHiddenFiles = false
op.prompt = "Allow"
op.title = "Allow access"
op.isExtensionHidden = true
op.directoryURL = URL(string: "/path/to/folder")
// Depending on your purpose, you might need these to true
op.allowsMultipleSelection = false
op.canChooseFiles = false