ios - 在不同 CollectionViewCell 之间传递数据

Question

我想将数据从 FeedCollectionViewCell 传递到另一个 ChatViewController。

内部 Feed View Controller

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellIdentifier, for: indexPath) as! FeedCollectionViewCell
cell.postTextView.text = posts.reversed()[indexPath.row].caption
cell.postImageView.image = UIImage(named: "photoplaceholder.jpg")
cell.priceTextView.text = posts.reversed()[indexPath.row].price
cell.categoryTextView.text = posts.reversed()[indexPath.row].category
cell.usernameLabel.text = posts.reversed()[indexPath.row].username
cell.buttonEvents = {
    let storyboard = UIStoryboard(name: "Main" , bundle: nil)
    let chatViewController =
        storyboard.instantiateViewController(withIdentifier: "chat")
    self.present(chatViewController, animated: true,completion: nil)
    var receiverIDNumber = cell.usernameLabel.text
}

//我想将receiverIDNumber传递给ChatViewController

ChatViewController 内部:

    func sendDataToDatabase(message: String){
    let ref = Database.database().reference()
    let senderIDNumber = Auth.auth().currentUser?.uid
    **//I want receiverIDNumber to be the data that is passed from  FeedViewController**
    let receiverIDNumber = "21"
    let postsReference = ref.child("chats")
    let newPostId = postsReference.childByAutoId().key
    let newPostReference = postsReference.child(newPostId)
    newPostReference.setValue(["message" : messageText.text!, "senderID" : senderIDNumber, "receiverID" : receiverIDNumber], withCompletionBlock: {
        (error, ref) in
        if error != nil {
            return
        }
    })
}

我正在尝试从 FeedCollectionViewCell 获取receiverIDNumber(将接收消息的用户)

对于MainViewController中的cell.buttonEvents来说，就是打开ChatViewController。

Main 的模型如下所示:

class Post{
var caption: String
var photoUrl: String
var price: String
var category: String
var username: String
var pic: String
init(captionText: String, photoUrlString: String, priceText: String, categoryText: String, usernameLabel: String, profileImageURL: String){
    caption = captionText
    photoUrl = photoUrlString
    price = priceText
    category = categoryText
    username = usernameLabel
    pic = profileImageURL
}

例如，在单元格中，用户个人资料图像旁边有一个按钮，人们可以单击该按钮与用户聊天。单击按钮后，它将引导他们到 ChatViewController。在 ChatViewController 中，我使用了不同的模型:

class Chat {
var message: String
var senderID: String
var receiverID: String

init(messageTextString: String, senderIDNumber: String, receiverIDNumber: String){
    message = messageTextString
    senderID = senderIDNumber
    receiverID = receiverIDNumber
}

由于接收者IDNumber(receiverUsername)来自ChatCollectionView，我发现很难将其与Main中的用户名协调起来。

Answer 1

首先，向您的 ChatViewController 类添加一个变量:

class ChatViewController: UIViewController {
    var username: String = ""

    override func viewDidLoad() {
        super.viewDidLoad()

        // Check if userID has been given a value
        if !username.isEmpty {
            // Do stuff here with username
        }
    }
}

然后您可以在实例化 View Controller 后为其分配一个值。我已将其放入 didSelectRow 方法中，因此当选择单元格时将出现新的 View Controller 。您仍然需要使用 cellForItemAt 方法创建每个单元格。

override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: IndexPath) {
    let storyboard = UIStoryboard(name: "Main" , bundle: nil)
    let chatViewController = storyboard.instantiateViewController(withIdentifier: "chat")
    // Here is the important bit
    chatViewController.username = posts.reversed()[indexPath.row].username
    // Present view controller
    self.present(chatViewController, animated: true,completion: nil)
}

一些注意事项:

• 不要在 cellForItemAt 方法中放置任何操作、 View Controller 演示等。每次重绘 Collection View 时，系统都会为每个项目调用它，所以这会很困惑。它仅用于设置每个单元格的外观。

• 创建一个新的反向帖子数组，而不是每次需要时都将其反转:let reveredPosts = posts.reversed()

• 我不确定您的 buttonEvents 做了什么。这是按下按钮时调用的闭包吗？这就是为什么我选择在选择单元格时呈现新的 View Controller 。

• 您还可以使用自定义 Storyboard Segue 来完成此操作，并使用以下方法:performSegue 呈现新的 View Controller ，使用 prepareForSegue 将数据发送到新 View Controller 出现之前。这将代替 self.present() 等。