Question

import UIKit

class KeyboardViewController: UIInputViewController, UIImagePickerControllerDelegate,     UINavigationControllerDelegate {

@IBOutlet var nextKeyboardButton: UIBarButtonItem
var statusLabel: UILabel  = UILabel()
var bottomBar : UIToolbar = UIToolbar()


var globeIcon : UIImage = UIImage(named: "globe-hover.png")
@IBOutlet var captureButton : UIBarButtonItem
@IBOutlet var libraryButton : UIBarButtonItem


override func viewDidLoad() {

    super.viewDidLoad()

    self.statusLabel.text="viewDidLoad() called"
    // Perform custom UI setup here
    self.nextKeyboardButton = UIBarButtonItem(image: self.globeIcon, style: .Plain , target: self, action: "advanceToNextInputMode")
    self.captureButton = UIBarButtonItem(title: "Take Photo", style: .Plain, target: self, action: "captureClicked")
    self.libraryButton = UIBarButtonItem(title: "Library", style: .Plain, target: self, action: "libraryClicked")

    self.statusLabel.setTranslatesAutoresizingMaskIntoConstraints(false)
    self.statusLabel.sizeToFit()



   var barItems : [UIBarButtonItem] = [self.nextKeyboardButton, self.captureButton, self.libraryButton]

    self.bottomBar.items = barItems
    self.view.addSubview(self.bottomBar)
    self.view.addSubview(self.statusLabel)



    var statusLabelLeftSideConstraint = NSLayoutConstraint(item: self.statusLabel, attribute: .Right, relatedBy: .Equal, toItem: self.view, attribute: .Right, multiplier: 1.0, constant: 0.0)
    var statusLabelBottomConstraint = NSLayoutConstraint(item: self.statusLabel, attribute: .Top, relatedBy: .Equal, toItem: self.view, attribute: .Top, multiplier: 1.0, constant: 0.0)
    self.view.addConstraints([statusLabelLeftSideConstraint, statusLabelBottomConstraint])





}

每次运行此操作时都会出现运行时错误：＆＃34;致命错误：在展开可选值时意外发现nil＆＃34;引用位var barItems : [UIBarButtonItem] = [self.nextKeyboardButton, self.captureButton, self.libraryButton]并且调试器声明barItems是一个空数组（nil）。

这里发生了什么？为什么数组barItems没有保存我的实例UIBarButtonItem变量？似乎UIBarButtonItem类型变量（captureButton，libraryButton和nextKeyboardButton）本身都是零，但为什么呢？提前谢谢！

Answer 1

来自目标C的许多对象都是隐式解包的选项，因为目标C指针不具有swift提供的相同类型安全性。

您在此行收到错误，因为类型[UIBarButtonItem]不允许数组中的nil值，而您在数组中放置的某些值是 {{1} }。

nil

我要做的第一件事就是让调试变得更简单，就是在这些值的原始实例化中添加类型（你期望var barItems : [UIBarButtonItem] = [self.nextKeyboardButton, self.captureButton, self.libraryButton]）：

nil

objective-c中的一些初始化器返回nil表示初始化失败，也许这就是这种情况？如果是，则在添加类型注释后会出现其他错误。你能发布那个错误吗？

swift数组不包含实例变量

1 个答案: