UIViewController的子类所需的初始值设定项

Question

我一直在尝试遵循有关创建容器视图控制器的教程.它在Objective-C中.我想将它转换为Swift.我在这里找到了一些相同的问题,但我没有从中得到太多.

这是代码.

import UIKit

class ContainerViewController: UIViewController { // Class "ContainerViewController" has no initializers - That I know why.

    // 'required' initializer 'init(coder:)' must be provided by a subclass of UIViewController

    var currentDetailViewController: UIViewController

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

}

我已经尝试过做两个错误所说的,但仍然无效.

Answer 1

问题是:如果声明任何存储的属性没有初始值,则必须实现自己的初始化程序来初始化它们.看到这个文件.

像这样:

var currentDetailViewController: UIViewController

override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
    currentDetailViewController = UIViewController()
    super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
}

convenience override init() {
    self.init(nibName: nil, bundle: nil)
}

required init(coder aDecoder: NSCoder) {
    currentDetailViewController = UIViewController()
    super.init(coder:aDecoder)
}

但是,我认为这不是你想要的.

正确的解决方案取决于您初始化的位置currentDetailViewController.

如果你总是在其中初始化它viewDidLoad,那么你可以将它声明为"隐式解包可选"

var currentDetailViewController: UIViewController!

override viewDidLoad() {
    super.viewDidLoad()
    self.currentDetailViewController = DetailViewController()
}

否则,如果currentDetailViewController可以nil,你应该声明它为"可选"

var currentDetailViewController: UIViewController?