您真的要隐藏/显示creeLigueBouton吗？相反，启用/禁用UIBarButtonItems要容易得多。您可以使用以下几行代码完成此操作：

if(condition == true) {
    creeLigueBouton.enabled = false
} else {
    creeLigueBouton.enabled = true
}

该代码甚至可以用更短的方式重写：

creeLigueBouton.enabled = !creeLigueBouton.enabled

让我们在UIViewController子类中查看它：

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var creeLigueBouton: UIBarButtonItem!

    @IBAction func hide(sender: AnyObject) {
        creeLigueBouton.enabled = !creeLigueBouton.enabled
    }

}

如果您确实想显示/隐藏creeLigueBouton，则可以使用以下代码：

import UIKit

class ViewController: UIViewController {

    var condition: Bool = true
    var creeLigueBouton: UIBarButtonItem! //Don't create an IBOutlet

    @IBAction func hide(sender: AnyObject) {
        if(condition == true) {
            navigationItem.rightBarButtonItems = []
            condition = false
        } else {
            navigationItem.rightBarButtonItems = [creeLigueBouton]
            condition = true
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        creeLigueBouton = UIBarButtonItem(title: "Creer", style: UIBarButtonItemStyle.Plain, target: self, action: "creerButtonMethod")
        navigationItem.rightBarButtonItems = [creeLigueBouton]
    }

    func creerButtonMethod() {
        print("Bonjour")
    }

}