TableViewCell数据传输，但数据在iOS中延迟到达

Question

我正在实现一个函数，当单击数据表单元格时，该函数会将单元格的标题发送到下一个控制器的JSON文件名。

数据传递得很好，但数据一个接一个地到达得很晚。如果单击第一个单元格，则数据不会消失；如果单击第二个单元格，将传输第一个单元格的内容。

我在哪里逐一调整迟到的数据？有什么想法吗？

vc1

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

guard let nextViewController: SecondViewController = segue.destination as? SecondViewController else {
return
}
guard let cell: UITableViewCell = sender as? UITableViewCell else {
return
}
nextViewController.title = cell.textLabel?.text
nextViewController.secondAssetName = jsonName
}

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
let country: Countries = countries[indexPath.row]
jsonName = country.asset_name
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return countries.count
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "MainCell", for: indexPath)
let country: Countries = countries[indexPath.row]
cell.imageView?.image = UIImage(named: "flag_" + country.asset_name)
cell.textLabel?.text = country.korean_name
return cell
}

// Data Transfer
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

guard let nextViewController: SecondViewController = segue.destination as? SecondViewController else {
return
}
guard let cell: UITableViewCell = sender as? UITableViewCell else {
return
}
nextViewController.title = cell.textLabel?.text
nextViewController.secondAssetName = jsonName
}
}

vc2

class SecondViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

var weathers = [Weather]()
var secondAssetName: String?

@IBOutlet weak var tableView: UITableView!


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

let jsonDecoder = JSONDecoder()
guard let dataAsset = NSDataAsset(name: secondAssetName ?? "") else {
return
}
do {
weathers = try jsonDecoder.decode([Weather].self, from: dataAsset.data)
} catch {
print(error.localizedDescription)
}
tableView.reloadData()
}

override func viewDidLoad() {
super.viewDidLoad()

self.tableView.delegate = self
self.tableView.dataSource = self
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return weathers.count
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell: CustomTableViewCell = tableView.dequeueReusableCell(withIdentifier: "CustomCell", for: indexPath) as! CustomTableViewCell
let weather: Weather = weathers[indexPath.row]

switch weather.state {
case 10:
cell.cellImageView?.image = UIImage(named: "sunny.png")
case 11:
cell.cellImageView?.image = UIImage(named: "cloudy.png")
case 12:
cell.cellImageView?.image = UIImage(named: "rainy.png")
case 13:
cell.cellImageView?.image = UIImage(named: "snowy.png")
default:
return cell
}
cell.cityNameLabel.text = weather.city_name
cell.temperatureLabel.text = String(weather.celsius)
cell.rainfallProbabilityLabel.text = String(weather.rainfall_probability)
return cell
}
}

Answer 1

为代码添加断点。你应该知道问题出在哪里。prepare(for: sender:)在tableView(_: didSelectRowAt:)之前被调用，所以第一次点击单元格时，jsonName在prepare期间为零，然后在didSelect期间被设置。第二次点击时，jsonName具有第一次点击时的值，然后更新。

把你所有的逻辑放在一个地方。删除didSelect方法，并更新prepare，如下所示：

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

guard let nextViewController: SecondViewController = segue.destination as? SecondViewController else {
return
}
guard let cell: UITableViewCell = sender as? UITableViewCell else {
return
}
guard let indexPath = tableView.indexPath(for: cell) else {
return
}
let country: Countries = countries[indexPath.row]
nextViewController.title = country.korean_name
nextViewController.secondAssetName = country.asset_name
}