Question

我有一个使用布局对象定义的CollectionViewController实例。

    let layout = UICollectionViewFlowLayout()
     (1)let friendsController = FriendsController(collectionViewLayout: layout)
    window?.rootViewController = UINavigationController(rootViewController: friendsController)

所以在friendsController中我已经定义了字符串属性消息。

class FriendsController: UICollectionViewController, UICollectionViewDelegateFlowLayout {
fileprivate let cellId = "cellId"
var messages: [Message]?


override func viewDidLoad() {

    super.viewDidLoad()
   navigationItem.title = "Recent"
   collectionView?.backgroundColor = UIColor.white
    collectionView?.register(MessageCell.self, forCellWithReuseIdentifier: cellId)
    collectionView?.alwaysBounceVertical = true
    setupData()

}
......

是的，我可以从（1）friendsController获取消息。但我定义了一个FriendController类的实例，它定义了空的初始化程序，但我无法获取消息属性。我曾建议我启动UIViewColletionController类的父类，但是当看到有关FriendController类的其他信息（使用空初始化程序初始化）时，它向我显示它仍然是 class FriendsController：UICollectionViewController，UICollectionViewDelegateFlowLayout。如果有人可以提示，那会对我有很大的帮助

Answer 1

1.解决方案：您可以在FriendsController

中创建自定义初始值设定项


class FriendsController: UICollectionViewController, UICollectionViewDelegateFlowLayout {
fileprivate let cellId = "cellId"
var messages: [Message]?

    init(collectionViewLayout layout: UICollectionViewLayout, and messages: [String]) {
        super.init(collectionViewLayout: layout)
        self.messages = messages
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }


    override func viewDidLoad() {

        super.viewDidLoad()
        navigationItem.title = "Recent"
        collectionView?.backgroundColor = UIColor.white
        collectionView?.register(MessageCell.self, forCellWithReuseIdentifier: cellId)
        collectionView?.alwaysBounceVertical = true
        setupData()

    }

然后

    let messages: [Message] = []
    let layout = UICollectionViewFlowLayout()
    let friendsController = FriendsController(collectionViewLayout: layout, and: messages)
    window?.rootViewController = UINavigationController(rootViewController: friendsController)

解决方案：只需在第一个代码中添加一行

    let messages: [Message] = []
    let layout = UICollectionViewFlowLayout()
    let friendsController = FriendsController(collectionViewLayout: layout, and: messages)
    friendsController.messages = messages
    window?.rootViewController = UINavigationController(rootViewController: friendsController)

为什么我不能从类的实例中获取属性？

1 个答案: