Apologies this is probably a real newbie question. I have some API code which goes away and calls a web service. When it returns I'd like to grab the value and display it in the UI but I'm struggling to see what means allows me to do this. I have this so far in my ViewController.....
'''
#IBAction func getToken(_ sender: NSButton) {
let cli = WSTokenServiceClient()
let rq = SecurityTokenRequest()
rq.UserName = "byname"
rq.Password = "abcdefg"
cli.GetUserWSToken(securityTokenRequest: rq, completionHandler: {(rep, err) in
NSLog(rep?.xmlResponseString ?? "none") //This successfully contains the string value I want
//token.stringValue = "jim" ///This doesn't work, it errors: NSControl.stringValue must be used from main thread only
})
}'''
I'd be grateful for any tips of where to go to solve this.
Thanks
You need
DispatchQueue.main.async {
self.token.stringValue = "jim"
}
Related
I have a CloudKit database with some data. By pressing a button my app should check for existence of some data in the Database. The problem is that all processes end before my app get the results of its search. I found this useful Answer, where it is said to use Closures.
I tried to follow the same structure but Swift asks me for parameters and I get lost very quick here.
Does someone can please help me? Thanks for any help
func reloadTable() {
self.timePickerView.reloadAllComponents()
}
func getDataFromCloud(completionHandler: #escaping (_ records: [CKRecord]) -> Void) {
print("I begin asking process")
var listOfDates: [CKRecord] = []
let predicate = NSPredicate(value: true)
let query = CKQuery(recordType: "Riservazioni", predicate: predicate)
let queryOperation = CKQueryOperation(query: query)
queryOperation.resultsLimit = 20
queryOperation.recordFetchedBlock = { record in
listOfDates.append(record)
}
queryOperation.queryCompletionBlock = { cursor, error in
if error != nil {
print("error")
print(error!.localizedDescription)
} else {
print("NO error")
self.Array = listOfDates
completionHandler(listOfDates)
}
}
}
var Array = [CKRecord]()
func generateHourArray() {
print("generate array")
for hour in disponibleHours {
let instance = CKRecord(recordType: orderNumber+hour)
if Array.contains(instance) {
disponibleHours.remove(at: disponibleHours.index(of: hour)!)
}
}
}
func loadData() {
timePickerView.reloadAllComponents()
timePickerView.isHidden = false
}
#IBAction func checkDisponibility(_ sender: Any) {
if self.timePickerView.isHidden == true {
getDataFromCloud{ (records) in
print("gotData")
self.generateHourArray()
self.loadData()
}
print(Array)
}
}
Im struggling to understand your code and where the CloudKit elements fit in to it, so Im going to try and give a generic answer which will hopefully still help you.
Lets start with the function we are going to call to get our CloudKit data, lets say we are fetching a list of people.
func getPeople() {
}
This is simple enough so far, so now lets add the CloudKit code.
func getPeople() {
var listOfPeople: [CKRecord] = [] // A place to store the items as we get them
let query = CKQuery(recordType: "Person", predicate: NSPredicate(value: true))
let queryOperation = CKQueryOperation(query: query)
queryOperation.resultsLimit = 20
// As we get each record, lets store them in the array
queryOperation.recordFetchedBlock = { record in
listOfPeople.append(record)
}
// Have another closure for when the download is complete
queryOperation.queryCompletionBlock = { cursor, error in
if error != nil {
print(error!.localizedDescription)
} else {
// We are done, we will come back to this
}
}
}
Now we have our list of people, but we want to return this once CloudKit is done. As you rightly said, we want to use a closure for this. Lets add one to the function definition.
func getPeople(completionHandler: #escaping (_ records: [CKRecord]) -> Void) {
...
}
This above adds a completion hander closure. The parameters that we are going to pass to the caller are the records, so we add that into the definition. We dont expect anyone to respond to our completion handler, so we expect a return value of Void. You may want a boolean value here as a success message, but this is entirely project dependent.
Now lets tie the whole thing together. On the line I said we would come back to, you can now replace the comment with:
completionHandler(listOfPeople)
This will then send the list of people to the caller as soon as CloudKit is finished. Ive shown an example below of someone calling this function.
getPeople { (records) in
// This code wont run until cloudkit is finished fetching the data!
}
Something to bare in mind, is which thread the CloudKit API runs on. If it runs on a background thread, then the callback will also be on the background thread - so make sure you don't do any UI changes in the completion handler (or move it to the main thread).
There are lots of improvements you could make to this code, and adapt it to your own project, but it should give you a start. Right off the bat, Id image you will want to change the completion handler parameters to a Bool to show whether the data is present or not.
Let me know if you notice any mistakes, or need a little more help.
Sorry, newbie here and Ive read extensively about completion handlers, dispatch queues and groups but I just can't get my head around this.
My app loads an array of Google Place IDs and then wants to query Google to get full details on each place. The problem is, due to async processing the Google Lookup Place returns immediately and the callback happens much further down the line so whats the "proper way" to know when the last bit of data has come in for my inquiries because the function ends almost immedately ?
Code is attached. Thanks in advance.
func testFunc() {
let googlePlaceIDs = ["ChIJ5fTXDP8MK4cRjIKzek6L6NM", "ChIJ9Wd6mGYGK4cRiWd0_bkohHg", "ChIJaeXT08ASK4cRkCGpGgzYpu8", "ChIJkRkS4BapK4cRXCT8-SJxNDI", "ChIJ3wDV_2zX5IkRtd0hg2i1LhE", "ChIJb4wUsI5w44kRnERe7ywQaJA"]
let placesClient = GMSPlacesClient()
for placeID in googlePlaceIDs {
placesClient.lookUpPlaceID(placeID, callback: { (place, error) in
if let error = error {
print("lookup place id query error: \(error.localizedDescription)")
return
}
guard let place = place else {
print("No place details for \(placeID)")
return
}
print("Place Name = \(place.name)")
})
}
print("Done")
}
I want to create a link, but when pressed it randomly chooses a link from a list. I have the code to take the button a link already, but how how would i modify it so I add more urls to it randomly choose when clicked different times.
Current link code:
#IBAction func Website(_ sender: Any) {
if let url = NSURL(string: "http:heeeeeeeey.com/"){
UIApplication.shared.openURL(url as URL)
}
}
Try something like:
#IBAction func Website(_ sender: Any) {
let websites = ["http://website1.com",
"http://website2.com",
"http://website3.com"]
if let url = URL(string: websites[Int(arc4random_uniform(UInt32(websites.count)))]) {
UIApplication.shared.openURL(url as URL)
}
}
This should do the trick for you.
Explanation:
websites is an array of Strings, so put all the URLs you want the button to pick from in there.
Int(arc4random_uniform(UInt32(websites.count))) is the magical part that picks a random number between 0 and websites.count(which is the last item you have in the array.
If you are new to Swift (or programming), this might sound confusing to you, don't freak out, just keep practicing.
Best of luck!
First, to create an array of URL strings is pretty straightforward:
var urls = [
"http://www.url1.com",
"http://www.url2.com",
"http://www.url3.com"
]
Now, you could get a random element of this urls array with this long line of code:
let randomURL = urls[Int(arc4random_uniform(UInt32(urls.count)))]
However, another way you could do it is to add an extension to Array that works on all arrays:
extension Array {
public var random: Element? {
let index = Int(arc4random_uniform(UInt32(self.count)))
return self.count>0 ? self[index] : nil
}
}
Now, getting a random element of the urls array is as easy as:
urls.random
This returns an Optional (this is because if there are no elements in an array, the random property will return nil). So in your code you'll also need to unwrap the result of the random property:
#IBAction func Website(_ sender: Any) {
if let urlString = urls.random,
let url = URL(string: urlString) {
UIApplication.shared.openURL(url as URL)
}
}
P.S. A couple of comments on your code:
I recommend you rename Website to openRandomWebsite (remembering to change the storyboard connections too). Methods should explain what they do, and begin with a lower case letter. If you're interested, Swift general code conventions here.
The openURL method has been deprecated in iOS 10, so I recommend you use the open(_:options:completionHandler:) method.
Your code would look like:
UIApplication.shared.open(url, options: [:], completionHandler: { (success) in
//URL opened
})
So I know this may be a bit specific but I've been staring at my code and am unable to resolve this issue. Basically, I'm making a network call to spotify to obtain a certain playlist and pass a number that will ultimately determine the number of songs I get back. The code is basically as follows:
// A network call is made just above to return somePlaylist
let playlist = somePlaylist as! SPTPartialPlaylist
var songs: [SPTPartialTrack] = []
// load in playlist to receive back songs
SPTPlaylistSnapshot.playlistWithURI(playlist.uri, session: someSession) { (error: NSError!, data: AnyObject!) in
// cast the data into a correct format
let playlistViewer = data as! SPTPlaylistSnapshot
let playlist = playlistViewer.firstTrackPage
// get the songs
for _ in 1...numberOfSongs {
let random = Int(arc4random_uniform(UInt32(playlist.items.count)))
songs.append(playlist.items[random] as! SPTPartialTrack)
}
}
The problem comes at the portion of code that initializes random. In maybe 1 in 20 calls to this function I, for whatever, reason unwrap a nil value for playlist.items.count and can't seem to figure out why. Maybe it's something I don't understand about API calls or something else I'm failing to see but I can't seem to make sense of it.
Anyone have any recommendations on addressing this issue or how to go about debugging this?
Ok, after sleeping on it and working on it some more I seem to have resolved the issue. Here's the error handling I implemented into my code.
if let actualPlaylist = playlist, actualItems = actualPlaylist.items {
if actualItems.count == 0 {
SongScraper.playlistHasSongs = false
print("Empty playlist, loading another playlist")
return
}
for _ in 1...numberOfSongs {
let random = Int(arc4random_uniform(UInt32(actualItems.count)))
songs.append(actualPlaylist.items[random] as! SPTPartialTrack)
}
completionHandler(songs: songs)
}
else {
print("Returned a nil playlist, loading another playlist")
SongScraper.playlistHasSongs = false
return
}
I'm trying to update a struct with multi-level nested async callback, Since each level callback provides info for next batch of requests till everything is done. It's like a tree structure. And each time I can only get to one level below.
However, the first attempt with inout parameter failed. I now learned the reason, thanks to great answers here:
Inout parameter in async callback does not work as expected
My quest is still there to be solved. The only way I can think of is to store the value to a local file or persistent store and modify it directly each time. And after writing the sample code, I think a global var can help me out on this as well. But I guess the best way is to have a struct instance for this job. And for each round of requests, I store info for this round in one place to avoid the mess created by different rounds working on the same time.
With sample code below, only the global var update works. And I believe the reason the other two fail is the same as the question I mentioned above.
func testThis() {
var d = Data()
d.getData()
}
let uriBase = "https://hacker-news.firebaseio.com/v0/"
let u: [String] = ["bane", "LiweiZ", "rdtsc", "ssivark", "sparkzilla", "Wogef"]
var successfulRequestCounter = 0
struct A {}
struct Data {
var dataOkRequestCounter = 0
var dataArray = [A]()
mutating func getData() {
for s in u {
let p = uriBase + "user/" + s + ".json"
getAnApiData(p)
}
}
mutating func getAnApiData(path: String) {
var req = NSURLRequest(URL: NSURL(string: path)!)
var config = NSURLSessionConfiguration.ephemeralSessionConfiguration()
var session = NSURLSession(configuration: config)
println("p: \(path)")
var task = session.dataTaskWithRequest(req) {
(data: NSData!, res: NSURLResponse!, err: NSError!) in
if let e = err {
// Handle error
} else if let d = data {
// Successfully got data. Based on this data, I need to further get more data by sending requests accordingly.
self.handleSuccessfulResponse()
}
}
task.resume()
}
mutating func handleSuccessfulResponse() {
println("successfulRequestCounter before: \(successfulRequestCounter)")
successfulRequestCounter++
println("successfulRequestCounter after: \(successfulRequestCounter)")
println("dataOkRequestCounter before: \(dataOkRequestCounter)")
dataOkRequestCounter++
println("dataOkRequestCounter after: \(dataOkRequestCounter)")
println("dataArray count before: \(dataArray.count)")
dataArray.append(A())
println("dataArray count after: \(dataArray.count)")
if successfulRequestCounter == 6 {
println("Proceeded")
getData()
}
}
}
func getAllApiData() {
for s in u {
let p = uriBase + "user/" + s + ".json"
getOneApiData(p)
}
}
Well, in my actual project, I successfully append a var in the struct in the first batch of callbacks and it failed in the second one. But I failed to make it work in the sample code. I tried many times so that it took me so long to update my question with sample code. Anyway, I think the main issue is to learn appropriate approach for this task. So I just put it aside for now.
I guess there is no way to do it with closure, given how closure works. But still want to ask and learn the best way.
Thanks.
What I did was use an inout NSMutableDictionary.
func myAsyncFunc(inout result: NSMutableDictionary){
let priority = DISPATCH_QUEUE_PRIORITY_DEFAULT
dispatch_async(dispatch_get_global_queue(priority, 0)) {
let intValue = result.valueForKey("intValue")
if intValue as! Int > 0 {
//Do Work
}
}
dispatch_async(dispatch_get_main_queue()) {
result.setValue(0, forKey: "intValue")
}
}
I know you already tried using inout, but NSMutableDictionary worked for me when no other object did.