swift - 从上一个 View 获取数据时如何分配同一类中相互使用的变量

Question

在加载此 Controller 之前，我有一个 View Controller ，它从我的数据库获取不同的视频并获取它们的下载网址，然后我使用 prepare(segue:... 将每个网址传递到它自己的字符串中的下一个 View Controller 。 )，在这个类中，我以编程方式使用自定义数据创建了一个 ScrollView ，但是我收到错误 Cannot use instance member 'itemOne' inside property initializer;属性初始值设定项在“self”可用之前运行。我理解这个错误的含义，并且我已经尝试过惰性变量，但考虑到以前的 View Controller 需要该变量来发送 url 数据(如果这有意义的话)，我认为它不会起作用。那么，当您需要将数据发送到该变量时，您会如何处理，这是我的代码:

class HomeViewController: UIViewController {

// Variables use with the previous view controller to send data between them

var itemOne: String? 
var itemTwo: String?
var itemThree: String?
var itemFour: String?

override func viewDidLoad() {
    super.viewDidLoad()

    view.addSubview(collectionView)
    collectionView.backgroundColor = .white
    collectionView.topAnchor.constraint(equalTo: view.topAnchor, constant: 150).isActive = true
    collectionView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 16).isActive = true
    collectionView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -16).isActive = true
    collectionView.heightAnchor.constraint(equalTo: collectionView.widthAnchor, multiplier: 0.5).isActive = true 

    collectionView.delegate = self
    collectionView.dataSource = self

}

fileprivate let data = [
    CustomData(title: "Test", image: #imageLiteral(resourceName: "ss-1"), url: itemOne!), // ERROR
    CustomData(title: "Test2", image: #imageLiteral(resourceName: "done-button"), url: itemTwo!), // ERROR
    CustomData(title: "Test2", image: #imageLiteral(resourceName: "notificationIcon"), url: itemThree!) // ERROR
]
/....

Answer 1

您可以使数据成为计算属性

var data: [CustomData] {
    return [
        CustomData(title: "Test", image: #imageLiteral(resourceName: "ss-1"), url: itemOne!),
        CustomData(title: "Test2", image: #imageLiteral(resourceName: "done-button"), url: itemTwo!),
        CustomData(title: "Test2", image: #imageLiteral(resourceName: "notificationIcon"), url: itemThree!)
    ]
}