Ios swift｜在具有自定义单元格的多个TableView中没有任何内容

这是我的密码.我判断了IBOulets连接、标识符、类名. 找到一些同舟共济的问题和答案.但没有说出话来. 我错过了什么吗？感谢您的阅读.:)

HomeViewController.swift个

import UIKit

struct Label {
    let top: String
    let day: String
    let summary: String
}

class HomeViewController: UIViewController {

    @IBOutlet weak var upperTableView: UITableView!
    @IBOutlet weak var lowerTableView: UITableView!
    
    let upperCellID = "UpperTableViewCell"
    let lowerCellID = "LowerTableViewCell"
    
    var dateString: String!
    
    var labels: [Label] = [
        Label(top: "title1", day: "2023.10.1.", summary: "Test"),
        Label(top: "title2", day: "2023.10.2.", summary: "Test"),
        Label(top: "title3", day: "2023.10.3.", summary: "Test")
    ]
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        
        // Upper Table (Your To-Do)
        upperTableView.delegate = self
        upperTableView.dataSource = self
        upperTableView.register(UpperTableViewCell.self, forCellReuseIdentifier: upperCellID)
        
        // Lower Table (Your To-Do)
        lowerTableView.delegate = self
        lowerTableView.dataSource = self
        lowerTableView.register(LowerTableViewCell.self, forCellReuseIdentifier: lowerCellID)
    }
    
    /*
     // MARK: - Navigation
     
     // In a storyboard-based application, you will often want to do a little preparation before navigation
     override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
     // Get the new view controller using segue.destination.
     // Pass the selected object to the new view controller.
     }
     */
    
}


extension HomeViewController: UITableViewDelegate, UITableViewDataSource {
    
    // These are working!
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        switch tableView {
        case upperTableView:
            print("you tabbed me!(Upper)")
        case lowerTableView:
            print("Below!")
        default:
            print("outside of table.")
        }
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return labels.count
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        
        var returnCell: UITableViewCell?
        
        if tableView == self.upperTableView {
            let cell = tableView.dequeueReusableCell(withIdentifier: self.upperCellID, for: indexPath) as! UpperTableViewCell
            cell.topLabel?.text = labels[indexPath.row].top
            returnCell = cell
        } else if tableView == lowerTableView {
            let cell = tableView.dequeueReusableCell(withIdentifier: self.lowerCellID, for: indexPath) as! LowerTableViewCell
            cell.titleLabel?.text = labels[indexPath.row].top
            returnCell = cell
        }
        return returnCell!
    }
}

UpperTableViewCell.swift个

import UIKit

class UpperTableViewCell: UITableViewCell {

    @IBOutlet weak var topLabel: UILabel!
    @IBOutlet weak var dateLabel: UILabel!
    @IBOutlet weak var summaryLabel: UILabel!
    
    override func awakeFromNib() {
        super.awakeFromNib()
        // Initialization code
    }

    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)

        // Configure the view for the selected state
    }

}

LowerTableViewCell.swift个

import UIKit

class LowerTableViewCell: UITableViewCell {

    @IBOutlet weak var titleLabel: UILabel!
    
    override func awakeFromNib() {
        super.awakeFromNib()
        // Initialization code
    }

    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)

        // Configure the view for the selected state
    }

}

我try 在上方和下方的TableView中显示标签. 但什么也没有出现.