tableView data source empty in viewDidLoad() - Swift - ios

Question

Below is my ViewController code. The println in GetRequest prints the correct data that it receives from the HTTP GET request. At this point, tableData has 10 key-value pairs. However, if I put a break point after the call to GetRequest() in viewDidLoad(), tableData is empty and nothing is displayed in the tableView. Why is this? Where am I going wrong?
import UIKit
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource
{
#IBOutlet var tableView: UITableView!
var tableData: [String:String] = [:]
let textCellIdentifier = "TextCell"
func GetRequest(urlPath: String)
{
var LatestWaitTimes: [String:String] = [:]
let url: NSURL = NSURL(string: urlPath)!
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithURL(url, completionHandler: {data, response, error -> Void in
if error != nil {
// If there is an error in the web request, print it to the console
println(error.localizedDescription)
}
var err: NSError?
var jsonResult: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: &err)
if err != nil {
// If there is an error parsing JSON, print it to the console
println("JSON Error \(err!.localizedDescription)")
}
let json = JSON(jsonResult!)
let count: Int? = json.array?.count
if let ct = count {
for index in 0...ct-1 {
let name = json[index]["CrossingName"].string
var wait = json[index]["WaitTime"].stringValue
if (wait == "-1")
{
wait = "No Info"
}
else
{
wait += " min"
}
println(name!+": "+wait)
LatestWaitTimes[json[index]["CrossingName"].stringValue] = wait as String?
}
}
self.tableData = LatestWaitTimes
})
task.resume()
}
override func viewDidLoad() {
super.viewDidLoad()
var apiInfo = GetWaitTimes()
GetRequest(apiInfo.BorderCrossingApi+"?AccessCode="+apiInfo.AccessCode)
self.tableView.delegate = self
self.tableView.dataSource = self
tableView.reloadData()
}
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return 1;
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return tableData.count
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var cell = tableView.dequeueReusableCellWithIdentifier(self.textCellIdentifier) as! UITableViewCell
let thisEntry = self.tableData.values.array[indexPath.row]
cell.textLabel?.text = thisEntry+": "+tableData[thisEntry]!
return cell
}
func tableView(tableView: UITableView, didDeselectRowAtIndexPath indexPath: NSIndexPath) {
tableView.deselectRowAtIndexPath(indexPath, animated: true)
}
}

Answer 1

The problem is that GetRequest runs asynchronously. So you have to reloadData inside the completionHandler of dataTaskWithURL:
let task = session.dataTaskWithURL(url, completionHandler: {data, response, error -> Void in
// do all of your existing stuff here
dispatch_async(dispatch_get_main_queue()) {
self.tableData = LatestWaitTimes
self.tableView.reloadData()
}
})
task.resume()
You can remove the reloadData from within viewDidLoad.

Answer 2

Rearrange the orders of the method calls:
override func viewDidLoad() {
super.viewDidLoad()
self.tableView.delegate = self
self.tableView.dataSource = self
var apiInfo = GetWaitTimes()
GetRequest(apiInfo.BorderCrossingApi+"?AccessCode="+apiInfo.AccessCode)
tableView.reloadData()
}
Explanation: you set the delegate and dataSource before you GetRequest() so the dataSource won't be nil.

Answer 3

Try this it may help you
you can add a callback (for reload tablview) in GetRequest function and run the callback after parser json in completionHandler
Maybe When you set the delegate with tableview, tableData still be nil (waitting for http response)
this is my code .you can refer to
demand.loadDataFromServer(self.view, done: { () -> Void in
self.demands = demand.getDemandDataList()
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.tableView.reloadData()
})
})
func loadDataFromServer(view:UIView,done:(() -> Void)!){
var request:HttpRequest = HttpRequest(view:view)
request.GET(getDemandListURL, parameters: nil, success: { (dict) -> Void in
self.demandLists = dict["data"] as NSMutableArray
done()
}, failed: { (dict) -> Void in
}) { (error) -> Void in
}
}