为什么UIBarButtonItem目标和操作归零?

I Want to press UIBarButtonItem programmatically in swift. I looked at the other questions asked in stackoverflow and did the same, but it didn't work.doing what i want when manually clicked but I need click programmatically. My example code is

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    let items =  self.navigationItem.rightBarButtonItems
    let item = items?.first


    UIApplication.shared.sendAction(item.action, to: item?.target, from: nil, for: nil) // not working


    _ = item.target?.perform(item.action, with: nil) // not working

    let action = item.action // result is  nil
    let target = item.target  / result is nil and item is not nil
}
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