我正在使用tableview控制器并尝试添加pull刷新功能，但在iPhone 5中测试pull to refresh功能时，在打开可选值错误时意外发现nil。错误发生在connectionDidFinishLoading函数处。
class FixtureTableTableViewController: UITableViewController,UITableViewDelegate,NSURLConnectionDelegate {
var fixtures:[Fixture] = []
var data = NSMutableData()
var jsonResults:NSArray! = nil
override func viewDidLoad() {
println("view did load")
super.viewDidLoad()
connectToServer();
self.refreshControl = UIRefreshControl()
//self.refreshControl?.attributedTitle = NSAttributedString(string: "pull to refresh")
self.refreshControl?.addTarget(self, action: Selector("refresh"), forControlEvents: UIControlEvents.ValueChanged)
//self.fixtures = Fixture().listAll()
// Uncomment the following line to preserve selection between presentations
// self.clearsSelectionOnViewWillAppear = false
// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem()
}
func refresh(){
println("refresh table")
fixtures = []
connectToServer()
self.refreshControl?.endRefreshing()
}
func connectToServer(){
println("connect to server")
let plist = NSBundle.mainBundle().pathForResource("hijaukuningapp",ofType: "plist")
let dict = NSDictionary(contentsOfFile: plist!)
var serverURL = dict["serverURL"] as String
println("server url (serverURL)")
let urlPath:String = serverURL + "mobileFixture/list"
println(urlPath)
var url = NSURL(string: urlPath)
var request = NSURLRequest(URL: url)
var connect = NSURLConnection(request: request, delegate: self, startImmediately: true)
connect.start()
}
func connection(connection: NSURLConnection, didReceiveData _data: NSData!){
println("receivedata")
data.appendData(_data)
println("end append data")
}
func connectionDidFinishLoading(connection: NSURLConnection){
println("finished loading data(data)")
var err: NSError
// throwing an error on the line below (can't figure out where the error message is)
jsonResults = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSArray
println(jsonResults)
fixtures = Fixture().listAll(jsonResults)
self.tableView.reloadData()
}
override func viewWillAppear(animated: Bool) {
println("viewWillAppear")
super.viewWillAppear(animated)
}
/*
override func viewWillAppear(animated: Bool) {
//startConnection();
println(jsonResults)
for result : AnyObject in jsonResults {
//println(result)
if let fixture = result as? Dictionary<String,AnyObject>{
var fixtureID = fixture["day"]
println(fixtureID)
var monthNamne = fixture["monthname"]
var tempFixture = Fixture()
tempFixture.day = fixtureID as String
tempFixture.month = monthNamne as String
var f2 = Fixture()
f2.homeTeam="KELANTAN"
f2.awayTeam = "KEDAH"
f2.venue = "STADIUM SULTAN MOHAMED, ALOR SETAR"
f2.day = "13"
f2.month = "OCT"
f2.time = "2045"
fixtures.append(f2)
self.tableView.reloadData()
}
println(fixtures.count)
}
}
*/
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// #warning Potentially incomplete method implementation.
// Return the number of sections.
return 1
}
override func tableView(tableView: UITableView?, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete method implementation.
// Return the number of rows in the section.
return fixtures.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("myCell", forIndexPath: indexPath) as FixtureTableViewCell
cell.lblVenue.text = fixtures[indexPath.row].venue
cell.lblHome.text = fixtures[indexPath.row].homeTeam.name
cell.lblAway.text = fixtures[indexPath.row].awayTeam.name
cell.lblDay.text = fixtures[indexPath.row].day
cell.lblMonth.text = fixtures[indexPath.row].month
cell.lblTime.text = fixtures[indexPath.row].time
var code:String = fixtures[indexPath.row].homeTeam.code + ".png"
var awayCode:String = fixtures[indexPath.row].awayTeam.code + ".png"
cell.homeLogo.image = UIImage(named: code);
cell.awayLogo.image = UIImage(named: awayCode)
return cell
}
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
println("indexpat " )
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {
println("prepare for sergues")
var detailController:FixtureDetailViewController = segue.destinationViewController as FixtureDetailViewController
var indexPath = self.tableView.indexPathForSelectedRow()
detailController.fixture = fixtures[indexPath!.row]
}
/*
// Override to support conditional editing of the table view.
override func tableView(tableView: UITableView!, canEditRowAtIndexPath indexPath: NSIndexPath!) -> Bool {
// Return NO if you do not want the specified item to be editable.
return true
}
*/
/*
// Override to support editing the table view.
override func tableView(tableView: UITableView!, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath!) {
if editingStyle == .Delete {
// Delete the row from the data source
tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
} else if editingStyle == .Insert {
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
}
}
*/
/*
// Override to support rearranging the table view.
override func tableView(tableView: UITableView!, moveRowAtIndexPath fromIndexPath: NSIndexPath!, toIndexPath: NSIndexPath!) {
}
*/
/*
// Override to support conditional rearranging of the table view.
override func tableView(tableView: UITableView!, canMoveRowAtIndexPath indexPath: NSIndexPath!) -> Bool {
// Return NO if you do not want the item to be re-orderable.
return true
}
*/
/*
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) {
// Get the new view controller using [segue destinationViewController].
// Pass the selected object to the new view controller.
}
*/
}
在这一行中，您的数据对象为nil。
jsonResults = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSArray
通过以下操作修复：
if let d = data {
//Only executed if data isn't nil
jsonResults = NSJSONSerialization.JSONObjectWithData(d, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSArray
}
在swift中，可选值意味着它可以为零。如果您没有从可选项中获得实际值，那么您的代码将无法编译。上面的模式只会在值不为零的情况下执行代码。