ios - 调用函数为类成员设置标签

Question

我在 UITableView 单元格 中有一组帖子。我创建了一个函数，以便当您单击单元格时，您会转到一个新的UIViewController。现在我希望新的 UIViewController 根据您单击的帖子更新正文和标题。我有新 UIViewController 的以下文本:

import UIKit
import Firebase
class MainTextView: UIViewController {
    @IBOutlet weak var titleText: UILabel!
    @IBOutlet weak var mainText: UILabel!

    func setMain(post:Post){
        titleText.text = post.text
        mainText.text = post.title
    }
}

以及我的主视图 Controller 的以下文本:

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    tableView.deselectRow(at: indexPath as IndexPath, animated: true)
    let row = indexPath.row
    print("Row: \(row)")
    let destination = storyboard!.instantiateViewController(withIdentifier: "MainTextView") as! MainTextView
    navigationController?.pushViewController(destination, animated: true)
    destination.setMain(post: posts[indexPath.row])
}

}

这是我的帖子类(class):

导入基金会

类帖子{ 变量 ID:字符串 var 标题:字符串 var 文本:字符串 var 创建时间:日期

init(id: String, title: String,text:String,  timestamp:Double) {
    self.id = id
    self.title = title
    self.text = text
    self.createdAt = Date(timeIntervalSince1970: timestamp / 1000)

}

}

我应该注意到，我在 HomeViewController 函数 fetchPost 中也收到以下错误:

 func fetchPosts(completion:@escaping (_ posts:[Post])->()) {
    let postsRef = Database.database().reference().child("posts")
    var queryRef:DatabaseQuery
    let lastPost = posts.last
    if lastPost != nil {
        let lastTimestamp = lastPost!.createdAt.timeIntervalSince1970 * 1000
        queryRef = postsRef.queryOrdered(byChild: "timestamp").queryEnding(atValue: lastTimestamp).queryLimited(toLast: 20)
    } else {
        queryRef = postsRef.queryOrdered(byChild: "timestamp").queryLimited(toLast: 20)
    }

    queryRef.observeSingleEvent(of: .value, with: { snapshot in
        var tempPosts = [Post]()

        for child in snapshot.children {
            if let childSnapshot = child as? DataSnapshot,
                let dict = childSnapshot.value as? [String:Any],
                let title = dict["text"] as? String,

                let text = dict["title"] as? String,
                let timestamp = dict["timestamp"] as? Double {

                if childSnapshot.key != lastPost?.id {
                    let post = Post(id: childSnapshot.key, title: title, text: text, timestamp:timestamp)
                    tempPosts.insert(post, at: 0)
                }

            }
        }

        return completion(tempPosts)
    })
}

这是我的 fetchPosts 函数:

func fetchPosts(completion: @escaping( _ posts:[Post])->()) {

        let postsRef = Database.database().reference().child("posts")
        let lastPost = self.posts.last
        var queryRef:DatabaseQuery

        if lastPost == nil {
            queryRef = postsRef.queryOrdered(byChild: "timestamp").queryLimited(toLast: 10)
        } else{
           let lastTimestamp = lastPost!.createdAt.timeIntervalSince1970 * 1000
            queryRef = postsRef.queryOrdered(byChild: "timestamp").queryEnding(atValue: lastTimestamp)
        }


        queryRef.observeSingleEvent(of: .value, with: {snapshot in

            var tempPosts = [Post]()

            for child in snapshot.children {
                if let childSnapshot = child as? DataSnapshot,
                    let dict = childSnapshot.value as? [String:Any],
                    let text = dict["text"] as? String,
                    let comment = dict["comment"] as? Array<String>,
                    let title = dict["title"] as? String,
                    let timestamp = dict["timestamp"] as? Double{
                    if childSnapshot.key != lastPost?.id {
                        let post = Post(id: childSnapshot.key, title: text, text: title, comment: comment, timestamp: timestamp)
                        tempPosts.insert(post, at: 0)
                    }

                }
            }
            return completion(tempPosts)

        })



    }

Answer 1

更改 MainTextView Controller 的逻辑:

import UIKit
import Firebase

class MainTextView: UIViewController {

  // MARK: - Your properties

  @IBOutlet weak var titleText: UILabel!

  @IBOutlet weak var mainText: UILabel!

  var post: Post?

  // MARK: - View Controller LifeCycle

  override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    self.setMain()
  }

  private func setMain() {
      guard let post = self.post else {
          return
      }

      titleText.text = post.text
      mainText.text = post.title
  }
}

您还应该更改 Controller 的逻辑

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
  tableView.deselectRow(at: indexPath as IndexPath, animated: true)

  if let destination = storyboard?.instantiateViewController(withIdentifier:"MainTextView") as? MainTextView {
      destination.post = <list of post>[indexPath.row]
      navigationController?.pushViewController(destination, animated: true)
  }
}

如果您在项目中使用 Segues，您可以尝试以下决定:

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
  tableView.deselectRow(at: indexPath as IndexPath, animated: true)
  performSegue(withIdentifier: "Your segue name", sender: self)
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "Your segue name", let destination = segue.destination as? MainTextView {
        destination.post = <Your selected post>
    }
}