伙计我从Foursquare APi获取数据，这里是我的代码。
但是我在cellForRowAtIndexPath上得到一个nil错误，因为venueItems是nil
proc->tf->esp = proc->tf->esp + 24;
*((uint*)(proc->tf->esp - 16)) = proc->tf->esp;
*((uint*)(proc->tf->esp - 12)) = proc->tf->esp;
*((uint*)(proc->tf->esp - 8)) = proc->tf->esp;
proc->tf->eip = *((uint*)(proc->tf->esp - 4));
我个人编程很新我认为venueItems是nil，因为class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
// Table View
self.tableView = UITableView()
// Location Manager Stuff
self.locationManager = CLLocationManager()
self.locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters
self.locationManager.delegate = self
let status = CLLocationManager.authorizationStatus()
if status == .notDetermined {
self.locationManager.requestWhenInUseAuthorization()
} else if status == CLAuthorizationStatus.authorizedWhenInUse
|| status == CLAuthorizationStatus.authorizedAlways {
self.locationManager.startUpdatingLocation()
} else {
showNoPermissionsAlert()
}
exploreVenues()
}
// Func's
func exploreVenues() {
guard let location = self.locationManager.location else {
return
}
var parameters = [Parameter.query: "Pubs"]
parameters += location.parameters()
let task = self.session.venues.explore(parameters) {
(result) -> Void in
if self.venueItems != nil {
return
}
if !Thread.isMainThread {
fatalError("!!!")
}
if let response = result.response {
if let groups = response["groups"] as? [[String: AnyObject]] {
var venues = [[String: AnyObject]]()
for group in groups {
if let items = group["items"] as? [[String: AnyObject]] {
venues += items
}
}
self.venueItems = venues
}
self.tableView.reloadData()
} else if let error = result.error, !result.isCancelled() {
self.showErrorAlert(error)
}
}
task.start()
}
// Table View Data source
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if let venueItems = self.venueItems {
return venueItems.count
}
return 10
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! VenueTableViewCell
// This is where the error occurs
let item = self.venueItems![(indexPath as NSIndexPath).row] as JSONParameters!
self.configureCellWithItem(cell, item: item!)
return cell
}
func configureCellWithItem(_ cell: VenueTableViewCell, item: JSONParameters) {
if let venueInfo = item["venue"] as? JSONParameters {
cell.nameLabel.text = venueInfo["name"] as? String
}
}
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
let cell = cell as! VenueTableViewCell
let tips = self.venueItems![(indexPath as NSIndexPath).row]["tips"] as? [JSONParameters]
guard let tip = tips?.first, let user = tip["user"] as? JSONParameters,
let photo = user["photo"] as? JSONParameters else {
return
}
let URL = photoURLFromJSONObject(photo)
if let imageData = session.cachedImageDataForURL(URL) {
cell.venueImageView.image = UIImage(data: imageData)
} else {
cell.venueImageView.image = nil
session.downloadImageAtURL(URL) { (imageData, error) -> Void in
let cell = tableView.cellForRow(at: indexPath) as? VenueTableViewCell
if let cell = cell, let imageData = imageData {
let image = UIImage(data: imageData)
cell.venueImageView.image = image
}
}
}
}
}
首先被执行。如果这是错误，我该如何修复它，以便在我的venueItems有一个值或任何其他更有效的方法之后运行cellForRowAtIndexpath中的代码？
答案 0 :(得分：4)
当numberOfRowsInSection为零时，10会返回self.venueItems。 self.venueItems似乎是零，直到您的网络请求完成，因此表视图已被告知它有10行显示要求每行的单元格。然后，您尝试强制解包可选属性（self.venueItems!）并崩溃。
看起来您的self.venueItems是可选的，有充分理由，请勿使用强制解包（!）丢弃该信息。当此属性为nil时，您可以返回0行，也可以将其初始化为非可选的空数组，然后您可以随时询问其count。
一般来说，这类问题你不想专注于阻止cellForRowAtIndexPath被调用，而是计划在任何时候调用它并返回一个合理的结果（比如报告该表有当你的后台任务还没有完成时，这就是0行。