Swift：从另一个选项卡中调用函数

I want to call the function

我想调用这个函数

 func setupChatLogForUser(user: ChatPartner){
    let layout = UICollectionViewFlowLayout()
    let chatLog = ChatHistory(collectionViewLayout: layout)
    chatLog.user = user
    navigationController?.pushViewController(chatLog, animated: true)
}
 func