I have a little app that downloads some names from the web, and then appends them to an array.
func fetchTitle(identifier: String, completion: (title: String) -> Void) {
let profileUrl = NSURL(string:"http://www.facebook.com/" + identifier)!
let task = NSURLSession.sharedSession().dataTaskWithURL(profileUrl) {
(data, response, error) -> Void in
if let urlContent = data {
let webContent = NSString(data: urlContent, encoding: NSUTF8StringEncoding)
let websiteArray = webContent!.componentsSeparatedByString("pageTitle\">")
let secondArray = websiteArray[1].componentsSeparatedByString("</title>")
let title = secondArray[0]
completion(title: title)
print(title)
}
}
task.resume()
}
//print(newArray)
var titles = [String]()
//let identifiers = ["100001986741004","100003866283798","100003455181526"]
let queue = dispatch_queue_create("titles", DISPATCH_QUEUE_SERIAL)
dispatch_apply(newArray.count, queue) { index in
let identifier = newArray[index]
fetchTitle(identifier) { title in
dispatch_async(queue) {
titles.append(title)
array.append(title)
}
}
}
I know it's pretty complicated, because it takes numbers from an array and turns them into names downloaded from the web, but never mind about that. The problem is, when I print title, it gives me the names, so I assume it does append them to the array, but when I print the array, it gives me no result.. I think this is because it takes a little while to download the data from the web, and the print happens immediately, but how to I delay the print (or display into table view) until the download is complete?
Any help is appreciated!
Thank you very much!
I don't know about swift, but when your data has been retrieved, in Objective-C you can call [tableView reloadData]; should be simple enough to translate to Swift
Related
I am following a tutorial on how to read and parse a csv file from dropbox in swift. However, the tutorial is 4 years old and my code is not compiling in swift5. The code example is copied below and the link to the original video tutorial is here https://www.youtube.com/watch?v=O6AKHAXpji0
I am getting two errors.
Error 1:
on the let request = line of callFileFromWeb(){}
'NSURL' is not implicitly convertible to 'URL'; did you mean to use 'as' to explicitly convert?
Error 2:
and on let session = ... within the httpGet(){}
'NSURLSession' has been renamed to 'URLSession'
When I try to implement the proposed fix for error two then I get another error
Cannot call value of non-function type 'URLSession`
Any ideas what should I be adjusting for it to work in swift5?
var items:[(days:String, city:String, inches: String)]?
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
callFileFromWeb()
}
func callFileFromWeb(){
let request = NSMutableURLRequest(URL: NSURL(string: "https://dl.dropboxusercontent.com/u/2813968/raindata.txt")!)
httpGet(request){
(data, error) -> Void in
if error != nil {
print(error)
} else {
print(data)//PRINTING ALL DATA TO CONSOLE
let delimiter = ":"
self.items = []
let lines:[String] = data.componentsSeparatedByCharactersInSet(NSCharacterSet.newlineCharacterSet()) as [String]
for line in lines {
var values:[String] = []
if line != "" {
values = line.componentsSeparatedByString(delimiter)
// Put the values into the tuple and add it to the items array
print(values[2])//PRINTING LAST COLUMN
let item = (days: values[0], city: values[1], inches: values[2])
self.items?.append(item)
}}//all good above
// self.AddDataToDatabase()
}//there was an error
}//end of request
}//end of get data from web and load in database
func httpGet(request: NSURLRequest!, callback: (String, String?) -> Void) {
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithRequest(request){
(data, response, error) -> Void in
if error != nil {
callback("", error!.localizedDescription)
} else {
let result = NSString(data: data!, encoding:
NSASCIIStringEncoding)!
callback(result as String, nil)
}
}
task.resume()
}
The final goal is to be able to read a file from drop box. The file updates weakly, so when users launch the app they always have access to the most updated version of the file, rather than having to re download the app when the file updates. Is this the correct approach to do this?
A framework that proved useful in past projects with parsing CSV files is:
CSwiftV -> https://github.com/Daniel1of1/CSwiftV
Updated: 9/23/2020
Let me demonstrate it by refactoring your callFileFromWeb():
func callFileFromWeb() {
let dropboxURL = URL(string: "https://dl.dropboxusercontent.com/u/2813968/raindata.txt")
URLSession.shared.dataTask(with: dropboxURL!) { data, response, error in
guard let urlData = data, error == nil else {
return
}
let unparsedCSV = String(data: urlData, encoding: String.Encoding.utf8) ?? "Year,Make,Model,Description,Price\r\n1997,Ford,E350,descrition,3000.00\r\n1999,Chevy,Venture,another description,4900.00\r\n"
let csv = CSwiftV(with: unparsedCSV)
let rows = csv.rows
var iteration = 0
for row in rows {
// Assuming you want the last row
if iteration == rows.count - 1 {
let item = (days: row[0], city: row[1], inches: row[2])
self.items?.append(item)
}
iteration += 1
}
}
}
One other thing, remember that you need to download CSSwiftV from Github and copy the original CSwiftV.swift file into your project.
Hope this helps!
I have an app that has species and photos. I am adding cloudKit to the app. I have a working solution, but now I need to add a completion handler as if the user downloads new species that include images, this takes some time (of course depending on how many images). However, the app allows the user to work during most of this process as it runs in the background.
The issue is if an image is not yet fully downloaded and the user select that species the app crashes, naturally.
I need to input a completion handler (or if someone has a better idea) that will allow me to use an activity indicator until the full process is completed. I found a few examples, but they don't take into account multiple download processes, like my images and thumbnails.
Here is my code. Note that I have removed some of the irrelevant code to reduce the amount shown.
func moveSpeciesFromCloud() {
let predicate = NSPredicate(value: true)
let query = CKQuery(recordType: RemoteRecords.speciesRecord, predicate: predicate)
CKDbase.share.privateDB.perform(query, inZoneWith: nil) {
records, error in
if error != nil {
print(error!.localizedDescription)
} else {
guard let records = records else { return }
for record in records {
DispatchQueue.main.async {
self.remoteVersion = record[RemoteSpecies.remoteSpeciesVersion] as! Int
self.remoteSpeciesID = record[RemoteSpecies.remoteSpeciesID] as! Int
self.speciesDetail = AppDelegate.getUserDatabase().getSpeciesDetails(self.remoteSpeciesID)
self.localVersion = self.speciesDetail.version
// being sure that remote version is newer than local version
if self.localVersion >= self.remoteVersion {
print("Species version not newer")
} else {
self.commonNameLabel = record[RemoteSpecies.remoteCommonName] as! String
self.speciesLabel = record[RemoteSpecies.remoteSpeciesName] as! String
self.genusLabel = record[RemoteSpecies.remoteGenusName] as! String
self.groupLabel = record[RemoteSpecies.remoteGroupName] as! String
self.subGroupLabel = record[RemoteSpecies.remoteSubGroupName] as! String
self.speciesDetailsLabel = record[RemoteSpecies.remoteSpeciesDetails] as! String
// Here I sync records to SQLite, but removed code as not relevant.
// now syncing Photos, Thumbs, Groups, SubGroups and Favorties
self.syncPhotosFromCloud(self.remoteSpeciesID)
self.syncThumbsFromCloud(self.remoteSpeciesID)
}
}
}
}
}
}
Here is the code for the Thumbnails (Images are same process)
func syncThumbsFromCloud(_ id: Int) {
let predicate = NSPredicate(format: "thumbSpeciesID = \(id)")
let query = CKQuery(recordType: RemoteRecords.thumbsRecord, predicate: predicate)
CKDbase.share.privateDB!.perform(query, inZoneWith: nil)
{
records, error in
if error != nil {
print(error!.localizedDescription)
} else {
guard let records = records else { return }
for record in records {
DispatchQueue.main.async {
self.thumbName = (record.object(forKey: RemoteThumbs.remoteThumbName) as? String)!
self.thumbID = (record.object(forKey: RemoteThumbs.remoteThumbID) as? Int)!
if let asset = record[RemoteThumbs.remoteThumbFile] as? CKAsset,
let data = try? Data(contentsOf: (asset.fileURL)),
let image = UIImage(data: data)
{
let filemgr = FileManager.default
let dirPaths = filemgr.urls(for: .documentDirectory,
in: .userDomainMask)
let fileURL = dirPaths[0].appendingPathComponent(self.thumbName)
if let renderedJPEGData = image.jpegData(compressionQuality: 1.0) {
try! renderedJPEGData.write(to: fileURL)
}
}
// syncing records to SQLite
AppDelegate.getUserDatabase().syncThumbsFromCloudToSQLite(id: self.thumbID, name: self.thumbName, speciesID: id)
}
}
}
}
}
I call it here on SyncVC:
#IBAction func syncCloudToDevice(_ sender: Any) {
let cloudKit = CloudKit()
cloudKit.moveSpeciesFromCloud()
cloudKit.moveFavoritessFromCloud()
}
If I missed a detail, please let me know.
Any assistance would be greatly appreciated.
I'm kind of concerned that both the previous answers don't help answer your question.. One is asking you to restructure your database and the other is asking you to become dependent on a third-party library.
My suggestion would be to make your perform(_:inZoneWith:) into a synchronous operation so that you can easily perform one after another. For example:
func performSynchronously(query: CKQuery) throws -> [CKRecord] {
var errorResult: Error?
var recordsResult: [CKRecord]?
let semaphore = DispatchSemaphore(value: 0)
CKDbase.share.privateDB!.perform(query, inZoneWith: nil) { records, error in
recordsResult = records
errorResult = error
semaphore.signal()
}
// Block this thread until `semaphore.signal()` occurs
semaphore.wait()
if let error = errorResult {
throw error
} else {
return recordsResult ?? []
}
}
Ensure that you call this from a background thread so as to not block your UI thread! For example:
// ... start your activity indicator
DispatchQueue(label: "background").async {
do {
let records1 = try performSynchronously(query: CKQuery...)
// parse records1
let records2 = try performSynchronously(query: CKQuery...)
// parse records2
DispatchQueue.main.async {
// stop your activity indicator
}
} catch let e {
// The error e occurred, handle it and stop the activity indicator
}
}
Of course, please just use this code as inspiration on how to use a semaphore to convert your asynchronous operations into synchronous ones. Here's a good article that discusses semaphores in depth.
Well, in general that sort of things are easy to do with RxSwift. You set activity indicator to on/off in .onSubscribe() and .onTerminated(), respectively, and you get the end result in subscriber/observer when it is ready. Specifically for CloudKit, you can use RxCloudKit library.
Is there a reason why you made the pictures a separate record type? I would just add the thumbnail and the full photo to the Species record type:
thumbnail = Bytes data type (1MB max)
photo = Asset data type (virtually limitless)
That way when you do your initial Species query, you will instantly have your thumbnail available, and then you can access the CKAsset like you are currently doing and it will download in the background. No second query needed which will make your code simpler.
I'm a little confused how would I parse a json API that gives me 20 objects but then gives me a key of "next" having a url that gives me another 20 objects. I'm using this Pokemon API. It gives me 4 keys: count, previous, results and next. I'm trying to display them all in a collection view but not all at the same time. I would like to load more when the collection view is scrolling down.
I'm just trying to get the name at the moment. This is how my code looks like.
I get it to load the first 20 Pokemon in the collection view. However I don't know how to load the next 20 Pokemon or the 20 after. This is how the json file looks like if the link didn't work.
I would appreciate any help given. :)
You can try using a recursive function reusing the loadPokemonsData function something like this:
func loadPokemonsData(url: String, quantity: Int?) {
let request = URLRequest(url: URL(string: url)!)
let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
if error != nil {
print(error!)
}
do {
let jsonResults = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as! NSDictionary
let pokemonArray = jsonResults.value(forKey: "results") as! [[String: Any]]
var isPokemonsEqualsToQuantity: Bool = false
for pokemonData in pokemonArray {
if let quantity = quantity {
guard self.pokemons.count < quantity else {
isPokemonsEqualsToQuantity = true
break
}
}
guard let name = pokemonData["name"] as? String else {
return
}
self.pokemon = Pokemon(name: name)
self.pokemons.append(self.pokemon)
}
guard let nextURL = jsonResults.value(forKey: "next") as? String, !isPokemonsEqualsToQuantity else {
for pokemon in self.pokemons {
print(pokemon.name)
}
print(self.pokemons.count)
return
}
self.loadPokemonsData(url: nextURL, quantity: quantity)
} catch let err as NSError {
print(err.localizedDescription)
}
}
task.resume()
}
Attach a screen of algorithm function running... it prints 791 pokemons.
Hope it helps you!
EDITED
Next time you ask put your code please... it will be easier help you!.
I've updated the code to set the quantity you want (nil if you want to get all pokemons), Therefore it will only get the pokemons in the order API returns it, if you want a specific pokemons from ALL pokemons you may do a sort after obtaining all pokemons.
if let toID = message.chatPartnerId() {
firebaseReference.child(toID).observeSingleEvent(of: .value, with: { (snapshot) in
if let dictionary = snapshot.value as? [String: Any] {
cell.nameLabel.text = dictionary["displayname"] as? String
let pic = dictionary["pictureURL"] as! String
print("THIS IS THE URL FOR EACH DISPLAYNAME")
print(dictionary["displayname"] as? String)
print(pic)
if let imageFromCache = MainPageVC.imageCache.object(forKey: pic as NSString) {
cell.pictureLabel.image = imageFromCache
} else {
let requested = URLRequest(url: URL(string: pic )!)
URLSession.shared.dataTask(with: requested) {data, response, err in
if err != nil {
print(err)
} else {
DispatchQueue.main.async {
let imageToCache = UIImage(data: data!)
MainPageVC.imageCache.setObject(imageToCache!, forKey: pic as NSString)
//cell.pictureLabel.image = nil
cell.pictureLabel.image = imageToCache
}
}
}.resume()
}
}
})
}
return cell
}
I'm running this code in my cellForRowAtIndexPath and I'm getting a ton of really bad behavior. I'm also getting similar behavior on other pages but for some reason this block of code with about a 90% consistency returns incorrect information for cells.
I get a lot of duplicate pictures being used, displaynames in the wrong places, but when I'm actually clicking into a person, my detail page shows the correct information every single time. That code is the typical didSelectRowAtIndexPath and passing the person.
What I don't understand is why on the initial load of this page all of the information is screwed up, but if I click into someone and come back the entire tableview has correct names and pictures. The names/pics also fix if I scroll a cell off the screen then come back to it.
I'm getting this behavior all over my app, meanwhile I see caching/loading done like this everywhere. Is it because I'm running the code in my cellForRowAtIndexPath? The only difference I see is that I'm running it there instead of creating a function inside of my Person class that configures cells and running it like that. What I don't understand is why that would make a difference because as far as I'm aware running a function within cellforRowAtIndexpath would be the same as copy-pasting that same code into there?
Any ideas/suggestions?
Edit: I'm getting a very similar situation when I'm running the following code:
self.PersonalSearchesList = self.PersonalSearchesList.sorted{ $0.users > $1.users }
self.tableView.reloadData()
Where I'm sorting my array before reloading my data. The information sometimes loads in incorrectly at first, but once I scroll the cell off the screen then come back to it it always corrects itself.
if you are using swift 3 here are some handy functions that allow you to save an image to your apps directory from an URL and then access it from anywhere in the app:
func saveCurrentUserImage(toDirectory urlString:String?) {
if urlString != nil {
let imgURL: URL = URL(string: urlString!)!
let request: URLRequest = URLRequest(url: imgURL)
let session = URLSession.shared
let task = session.dataTask(with: request, completionHandler: {
(data, response, error) -> Void in
if (error == nil && data != nil) {
func display_image() {
let userImage = UIImage(data: data!)
if let userImageData = UIImagePNGRepresentation(userImage!) {
let filename = self.getDocumentsDirectory().appendingPathComponent("userImage")
try? userImageData.write(to: URL(fileURLWithPath: filename), options: [.atomic])
}
}
DispatchQueue.main.async(execute: display_image)
}
})
task.resume()
}
}
and then access it with any view controller using this:
extension UIViewController {
func getImage(withName name: String) -> UIImage {
let readPath = getDocumentsDirectory().appendingPathComponent(name)
let image = UIImage(contentsOfFile: readPath)
return image!
}
}
and finally calling it like this:
cell.pictureLabel.image = getImage(withName: "userImage")
If you can run the saveCurrentUserImage function prior to running cellForRowAtIndexPath then you can just check if the photo is nil in the directory before attempting to download it. You might be getting funny behavior when the page initially loads because you have multiple network calls going on at once. I wouldn't recommend making any network calls in cellForRowAtIndexPath because every time the cells are re-initialized it's going to make that network call for each cell.
Hope it helps!
EDIT: This method of image saving and retrieval is for images that you want to persist. If you want to erase them from memory you'll have to delete them from your directory.
I'm hoping someone an help me figure out a problem that has me scratching my brain! When I attempt this function using a NSData(contentsOfUrl... structure, this all works fine. However, I am attempting to use a NSURLSession for use on an Apple Watch app, and keep hitting an error;
...
class func fetchData() -> [Complication] {
var task: NSURLSessionDataTask?
let myURL = "http://www.myurl.com/sample.json"
let dataURL = NSURL(string: myURL)
let conf = NSURLSessionConfiguration.defaultSessionConfiguration()
conf.requestCachePolicy = NSURLRequestCachePolicy.ReloadIgnoringCacheData
let session = NSURLSession(configuration: conf)
task = session.dataTaskWithURL(dataURL!) { (data, res, error) -> Void in
if let e = error {
print("dataTaskWithURL fail: \(e.debugDescription)")
return
}
var dataSet = [Complication]()
do {
let json = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers) as! NSArray
for item in json {
let name: String? = item["name"] as? String
let percent: Int? = item["percent"] as? Int
let timeFromNow: Int? = item["timeFromNow"] as? Int
let myData = Complication(
name: name!,
percent: percent!,
timeFromNow: timeFromNow!
)
dataSet.append(myData)
}
} catch {
print(error)
}
}
return dataSet
//THIS LINE THROWS THE ERROR
}
...
When attempting to return my dataSet array, I receive the error Instance member 'dataSet' cannot be used on type 'Complication'. As mentioned, however, this does seem to work if I were to use a NSData(contentsOfUrl... instead of a NSURLSession, which is where I am stuck!
The data task is a closure that is executed asynchronously. Its return statements returns from the closure, not from the outer function.
Since the closure is executed asynchronously it makes no sense to return data from it: the return type is Void.
You should organize your code differently, e.g. using a completion handler.
Hint: search for "swift return closure" in SO. You will find plenty of questions similar to yours and a number of good answers and suggestions.