swift what is the timing to reload data after NSURLSession POST request - ios

Question

I am trying to show some data in tableView after getting JSON. However, it is failed by using tableView.reloadData() . I menu delay.
My situation is that the tableView will reload data after 14-20 seconds of getting JSON, but it will reload data immediately when user active the table.
Swift:
func getJson(word: String){
let url: NSURL = NSURL(string: "MyPHP.php")!
let session = NSURLSession.sharedSession()
let request:NSMutableURLRequest = NSMutableURLRequest(URL:url)
request.HTTPMethod = "POST"
request.cachePolicy = NSURLRequestCachePolicy.ReloadIgnoringCacheData
let bodydata = "label=\(word)"
request.HTTPBody = bodydata.dataUsingEncoding(NSUTF8StringEncoding)
if bodydata != " " {
let task = session.dataTaskWithRequest(request) {
(data, response, error) -> Void in
let httpResponse = response as! NSHTTPURLResponse
let statusCode = httpResponse.statusCode
if(statusCode == 200) {
self.libraryArray.removeAll()
do{
let json = try NSJSONSerialization.JSONObjectWithData(data!, options:.AllowFragments)
print(json)
if let book = json["Book"] as? [[String: AnyObject]]{
for books in book {
if let BookName = book["Name"] as? [String: AnyObject] {
let name = BookName["name"] as? String
let author = BookName["author"] as? String
let bookDict = [
"name": name,
"id": id,
"author": author]
self.libraryArray.append(bookDict)
self.tableView.reloadData() // has 14- 20 seconds delay, but the JSON has already received
}
}
}
}catch {
print("error:\(error)")
}
}
}
task.resume()
// self.tableView.reloadData() if i try to reload here, it will not be executed.
}
}
#IBAction func Next(sender: AnyObject) {
self.getJson("someString")
//self.tableView.reloadData() if i try to reload here, it will be fail.
}
what is the problem of the delay? How to solve it?
What is the right timing to reload tableView?

Answer 1

Replace your self.tableView.reloadData() with this
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.tableView.reloadData()
})

Answer 2

You are asking the table to reload while you didn't finish parsing the json. you do that after every Book parsing. you should do it after you finish parsing. the only explanation of the delay is that you have a huge data that is taking all that time for parsing!! Is that possible?
func getJson(word: String){
let url: NSURL = NSURL(string: "MyPHP.php")!
let session = NSURLSession.sharedSession()
let request:NSMutableURLRequest = NSMutableURLRequest(URL:url)
request.HTTPMethod = "POST"
request.cachePolicy = NSURLRequestCachePolicy.ReloadIgnoringCacheData
let bodydata = "label=\(word)"
request.HTTPBody = bodydata.dataUsingEncoding(NSUTF8StringEncoding)
if bodydata != " " {
let task = session.dataTaskWithRequest(request) {
(data, response, error) -> Void in
let httpResponse = response as! NSHTTPURLResponse
let statusCode = httpResponse.statusCode
if(statusCode == 200) {
self.libraryArray.removeAll()
do{
let json = try NSJSONSerialization.JSONObjectWithData(data!, options:.AllowFragments)
print(json)
if let book = json["Book"] as? [[String: AnyObject]]{
for books in book {
if let BookName = book["Name"] as? [String: AnyObject] {
let name = BookName["name"] as? String
let author = BookName["author"] as? String
let bookDict = [
"name": name,
"id": id,
"author": author]
self.libraryArray.append(bookDict)
self.tableView.reloadData() // has 14- 20 seconds delay, but the JSON has already received
}
}
}
}catch {
print("error:\(error)")
}
self.tableView.reloadData() // <<----- HERE
}
}
task.resume()
// self.tableView.reloadData() if i try to reload here, it will not be executed.
}
}
#IBAction func Next(sender: AnyObject) {
self.getJson("someString")
//self.tableView.reloadData() if i try to reload here, it will be fail.
}