NSUrlSession Running Slow in Swift - ios

In swift I am downloading data in swift to my iOS app. It works just fine although what ends up happening is it can take up to 20 seconds for it to load even though I am on a fast connection. I don't understand why this happens. I was almost thinking about downloading all the data before the app opens although I don't want to do that because I know it is possible to speed it up which I know is possible because apps like YouTube and Facebook can load and refresh in less than 20 seconds. Heck, YouTube loads videos in less then that amount of time. I know my server isn't as fast as there's but I do happen to know my server is faster then that. I do want to remind you that the page does end up loading just not quickly. Please help. Here is the NSUrlSession code.
func contactApiUrl(){
let url = "http://www.example.com"
let nsUrl = NSURL(string:url)
let nsUrlRequest = NSURLRequest(URL: nsUrl!)
let task = NSURLSession.sharedSession().dataTaskWithRequest(nsUrlRequest){
(data, response, error) in
if let dat = data{
let contents = NSString(data:dat, encoding:NSUTF8StringEncoding) as! String
self.aboutText.text = contents
}
}
task.resume()
}
I want to thank anybody who can help me with this in advance.

func contactApiUrl(){
guard
let nsUrl = NSURL(string: "http://www.example.com")
else { return }
NSURLSession.sharedSession().dataTaskWithRequest(NSURLRequest(URL: nsUrl)){
(data, response, error) in
guard
let data = data,
let contents = String(data: data, encoding: NSUTF8StringEncoding)
else { return }
// All UI updates should be done at the main queue.
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.aboutText.text = contents
})
}.resume()
}

Related

Showing image from URL in iOS app [duplicate]

This question already has answers here:
Loading/Downloading image from URL on Swift
(39 answers)
Closed 5 years ago.
EDIT 3: Please also read my comment in the "answered" tagged answer. I think I won't use my synchronous method but change to the suggested asynchronous methods that were also given!
Ok I am struggling with some basic concepts of showing images from an URL from the internet on my app.
I use this code to show my image on an UIIamgeView in my ViewController:
func showImage() {
let myUrlImage = URL(string: linkToTheImage)
let image = try? Data(contentsOf: myUrlImage!)
imageView1.image = UIImage(data: image!)
}
Now basically I have the following question:
Is the whole image downloaded in this process?
Or works the UIImageView like a "browser" in this case and doesn't download the whole picture but only "positions" the image from the URL into my UIImageView?
EDIT:
The reason I asked is, I am basically doing a quiz app and all I need in the view is an image from a URL for each question - so it's no difference if I do it asynchronous or synchronous because the user has to wait for the image anyways. I am more interested in how do I get the fastest result:
So I wanted to know if my code really downloads the picture as a whole from the URL or just "Positions" it into the UIImageView?
If in my code the picture is downloaded in its full resolution anyways, then you are right, I could download 10 pictures asynchronously when the player starts the quiz, so he hopefully doesn't have to wait after each answer as long as he would wait when I start downloading synchronously after each answer.
Edit 2:
Because my Question was tagged as similar to another some more explanation:
I already read about synchronous and asynchronous downloads, and I am aware of the downsides of synchronous loading.
I am more interested in a really basic question, and I get the feeling I had one basic thing really wrong:
My initial thought was that if I open a link in my browser, for example this one,
https://cloud.netlifyusercontent.com/assets/344dbf88-fdf9-42bb-adb4-46f01eedd629/68dd54ca-60cf-4ef7-898b-26d7cbe48ec7/10-dithering-opt.jpg
the browser doesn't download the whole picture. But I guess this isn't the case? The whole picture is downloaded?
Never use Data(contentsOf:) to display data from a remote URL. That initializer of Data is synchronous and is only meant to load local URLs into your app, not remote ones. Use URLSession.dataTask to download image data, just as you would with any other network request.
You can use below code to download an image from a remote URL asynchronously.
extension UIImage {
static func downloadFromRemoteURL(_ url: URL, completion: #escaping (UIImage?,Error?)->()) {
URLSession.shared.dataTask(with: url) { data, response, error in
guard let data = data, error == nil, let image = UIImage(data: data) else {
DispatchQueue.main.async{
completion(nil,error)
}
return
}
DispatchQueue.main.async() {
completion(image,nil)
}
}.resume()
}
}
Display the image in a UIImageView:
UIImage.downloadFromRemoteURL(yourURL, completion: { image, error in
guard let image = image, error == nil else { print(error);return }
imageView1.image = image
})
You can do it this way. But in most cases it is better to download the image first by yourself and handle the displaying then (this is more or less what the OS is doing in the background). Also this method is more fail proof and allows you to respond to errors.
extension FileManager {
open func secureCopyItem(at srcURL: URL, to dstURL: URL) -> Bool {
do {
if FileManager.default.fileExists(atPath: dstURL.path) {
try FileManager.default.removeItem(at: dstURL)
}
try FileManager.default.copyItem(at: srcURL, to: dstURL)
} catch (let error) {
print("Cannot copy item at \(srcURL) to \(dstURL): \(error)")
return false
}
return true
}
}
func download() {
let storagePathUrl = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as NSString).appendingPathComponent("image.jpg")
let imageUrl = "https://www.server.com/image.jpg"
let urlRequest = URLRequest(url: URL(string: imageUrl)!)
let task = URLSession.shared.downloadTask(with: urlRequest) { tempLocalUrl, response, error in
guard error == nil, let httpResponse = response as? HTTPURLResponse, httpResponse.statusCode == 200 else {
print("error")
return
}
guard FileManager.default.secureCopyItem(at: tempLocalUrl!, to: storagePathUrl) else {
print("error")
return
}
}
task.resume()
}

URLSession results in NIL data

I'm trying to learn Swift, and I have a little project with Google's places API.
I have a method for fetching places details, which uses URLSession in swift to send the request:
func fetchRestaurantDetails(placeId: String) -> Void {
let jsonURLString = "https://maps.googleapis.com/maps/api/place/details/json?placeid=\(placeId)&key=[MY API KEY]"
guard let url = URL(string: jsonURLString) else { return}
let urlRequest = URLRequest(url: url)
// set up the session
let config = URLSessionConfiguration.default
let session = URLSession(configuration: config)
_ = session.dataTask(with: urlRequest) { (data, response, error) in
// check for any errors
guard error == nil else {
print("error calling GET on /todos/1")
print(error!)
return
}
// make sure we got data
guard let responseData = data else {
print("Error: did not receive data")
return
}
// parse the result as JSON, since that's what the API provides
do {
let place = try JSONDecoder().decode(Result.self, from: responseData) // New in Swift 4, used to serialize json.
self.rest = place.result
} catch {
print("error trying to convert data to JSON")
return
}
}.resume()
}
I use this method to create a instance of type Restaurants, which I will later add to a list:
func createRestaurant(placeId: String) -> Restaurants {
self.fetchRestaurantDetails(placeId: placeId)
let rest = Restaurants(name: self.rest.name,
formatted_address: self.rest.formatted_address,
website: self.rest.website,
location: ((self.rest.geometry.location.lat,self.rest.geometry.location.lng)),
opening_hours: self.rest.opening_hours.weekday_text,
photo: restImg)
return rest!
}
But whenever I reach back into the "let rest = Restaurants(...)" all the values are nil. When I try to debug it, it just jumps over my "_ = session" sections right down to resume(), then back to session again and ends back at resume(). No data produced.
I'm quite puzzled since I successfully executed this piece of code before, and now I'm wondering if I missed something.
Thx :-)
Put two breakpoints. One at
let place = try JSONDecoder().decode(Result.self, from: responseData) // New in Swift 4, used to serialize json.
self.rest = place.result
and the second one at
let rest = Restaurants(name: self.rest.name,
formatted_address: self.rest.formatted_address,
website: self.rest.website,
location: ((self.rest.geometry.location.lat,self.rest.geometry.location.lng)),
opening_hours: self.rest.opening_hours.weekday_text,
photo: restImg)
You will realise that the second one is getting called first.
You are fetching data, which is done asynchronously, and before its available you are trying to use it. You need to make sure that the data is available before you use it. One way here would be to use completion handler. You can learn about completion handlers here.
fetchRestaurantDetails is an asynchronous method due to the fact that you call session.dataTask in it, which is asynchronous.
You are trying to use the results of the function before it actually returned. You have several ways to solve this issue:
Use a completion handler to return the value from fetchRestaurantDetails
Use DispatchGroups to detect when the URLRequest finished
Use a 3rd party framework like PromiseKit to handle the asynchronous functions like normal functions with return values.

Image URL to UIImage Not Working

let url = URL(string: (pinsFIREBASE[marker.snippet!]?.imageURL)!)
let task = URLSession.shared.dataTask(with: url!) { data, response, error in
guard let data = data, error == nil else { return }
DispatchQueue.main.async() {
self.postImage.image = UIImage(data: data)
}
}
task.resume()
I have the following code that takes a url from firebase, in the form http://i.imgur.com/nkomPpP.jpg, and is supposed to turn that url into a UIImage that can be placed on a view. However, while extracting the text from the firebase object works, parsing the image URL doesn't seem to be working as I get an empty view. What am I doing wrong?
I know why, your code works. The problem is your image link. Your imageURL's HTTP type. iOS don't like HTTP type request because it's not safe.
Plan A: Try a HTTPS type image link, it works.
Plan B: Add "App Transport Security Settings" in project info ,and set "Allow
Arbitrary Loads" yes in "App Transport Security Settings" dictionary.
I suggested use Plan A, that's Apple want iOSDev to do.
You need to remove the () from after DispatchQueue.main.async(). Try this:
let url = URL(string: (pinsFIREBASE[marker.snippet!]?.imageURL)!)
let task = URLSession.shared.dataTask(with: url!) { data, response, error in
guard let data = data, error == nil else { return }
DispatchQueue.main.async {
self.postImage.image = UIImage(data: data)
}
}
task.resume()

Swift 3: failed url request and image not being adding to cell

I'm trying to load some pictures from different URL in order to add them to my Table View Cells. Each cell contains an UIImageView and the pictures (UIImage) are not loading correctly.
Sometimes the URL connection fails, and sometimes not. I'm going crazy,
help me please!!
This is the part of my code that tries to download a picture from an specific URL:
let imageURL = NSURL(string: "https://upload.wikimedia.org/wikipedia/commons/thumb/9/98/Angels_Stadium.JPG/1920px-Angels_Stadium.JPG")!
let task = URLSession.shared.dataTask(with: imageURL as URL) { (data, response, error) in
guard error == nil, let data = data else { return }
let downloadedImage = UIImage(data: data)
self.foto = downloadedImage!
tableWiew.reloadData()
}
task.resume()
This code is inside the init function of my class (User). After instantiate the class, I try to add the picture to my tableview in other class like this:
let user:User = User(json: obj, tableWiew: self.tableView)
addCell(cell: cell, name: user.nombre, job: user.puesto, nIdeas: "0", mProp: "0", image: user.foto)
The "addCell" method just creates a custom cell and inserts it into my tableView. That's working fine except for the damn picture.
If I add a picture from my Assets it works fine, but I don't know what's wrong when I try to add a picture from an URL.
Please download an image inside cellForRowAt method of UITableViewDataSource and if possible use SDWebImage that will help you with many options eg placeholder. It handles the caching internally and it is async.
let imageURL = NSURL(string: "https://upload.wikimedia.org/wikipedia/commons/thumb/9/98/Angels_Stadium.JPG/1920px-Angels_Stadium.JPG")!
let request = URLRequest(url: imageURL as URL)
let session = URLSession.shared
let task = session.dataTask(with: request, completionHandler: {data, response, error -> Void in
// print("Task completed")
// print(response)
DispatchQueue.main.async(execute: {
self.imgVW.image = UIImage(data: data!)
})
})
task.resume()

Images loading in incorrectly even with cache

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.

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