iOS Swift fetching more data for collection view after having navigated to detail view not working - ios

Question

I am working on an assignment for a job interview. I have finished most of the assignment. There's only a bug i can't figure out. I have been trying for three days now.
I had to make a client app for the Flickr API that allows users to search for photos using specific words. Display the results in a collection view with infinite scroll. And when a photo is selected it should show the details of the photo in a detail view.
The bug:
Everything is working if i stay in the collection view. I can search over and over again and the infinite scroll is also working.As soon as a specific index in the index path is hit. A new request is sent with the same search term. But if i select a photo and then navigate back to the collection view and try a new search nothing comes back and my error handeling returns an error. (the error is not a console error).Also when navigating back from detail to collection. I can still scroll until the index triggers a new request than it also throws an error.
I hope i am explaining it well. I am really getting desperate at the moment. I tried everything i could think of: the request url still works when i try it in the browser.
Please help! If you need more info just ask.
Collection view controller:
import UIKit
// Global variable for holding a search term.
var searchTerm: String?
// Global variable to hold an instance of Reachability.
var reachability: Reachability?
// Enum for changing the textfield placeholder text.
enum TextFieldPlaceHolderText: String {
case Search = "Search"
case Searching = "Searching..."
}
class PhotosViewController: UIViewController {
// MARK: - Outlets
#IBOutlet var collectionView: UICollectionView!
#IBOutlet var searchTextField: UITextField!
// MARK: - Properties
let photoDataSource = PhotoDataSource()
let photoStore = PhotoStore()
// MARK: - View Setup
override func viewDidLoad() {
super.viewDidLoad()
// Sets the data source and delegate.
collectionView.dataSource = photoDataSource
collectionView.delegate = self
// Uses an image to add a pattern to the collection view background.
collectionView.backgroundColor = UIColor(patternImage: UIImage(named: "flickr.png")!)
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
// Checks if the device is connected to the internet.
checkForReachability()
}
// MARK: showAlert
func showAlert(title: String, message: String) {
let alert = UIAlertController(title: title, message: message, preferredStyle: .Alert)
let okAction = UIAlertAction(title: "Ok", style: .Cancel, handler: { (nil) in
self.dismissViewControllerAnimated(true, completion: nil)
})
alert.addAction(okAction)
self.presentViewController(alert, animated: true, completion: nil)
}
// MARK: - Segue
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "ShowPhoto" {
if let selectedIndexPath = collectionView.indexPathsForSelectedItems()?.first {
let flickrPhoto = photoDataSource.flickrPhotos[selectedIndexPath.row]
let destinationVC = segue.destinationViewController as! PhotoDetailViewController
destinationVC.flickrPhoto = flickrPhoto
destinationVC.photoStore = photoStore
}
}
}
// MARK: - checkForReachability
func checkForReachability() {
do {
reachability = try Reachability.reachabilityForInternetConnection()
} catch {
print("Unable to create Reachability")
return
}
reachability!.whenReachable = { reachability in
// This is called on a background thread, but UI updates must be on the main thread.
NSOperationQueue.mainQueue().addOperationWithBlock({
if reachability.isReachableViaWiFi() {
print("Reachable via WiFi")
} else {
print("Reachable via Cellular")
}
})
}
reachability!.whenUnreachable = { reachability in
// This is called on a background thread, but UI updates must be on the main thread.
NSOperationQueue.mainQueue().addOperationWithBlock({
print("Not reachable")
self.showAlert("No Internet Connection", message: "Make sure your device is connected to the internet.")
})
}
do {
try reachability!.startNotifier()
} catch {
print("Unable to start notifier")
}
}
}
//MARK: - Extension UICollectionViewDelegate
extension PhotosViewController: UICollectionViewDelegate {
//MARK: - willDisplayCell
func collectionView(collectionView: UICollectionView, willDisplayCell cell: UICollectionViewCell, forItemAtIndexPath indexPath: NSIndexPath) {
let flickrPhoto = photoDataSource.flickrPhotos[indexPath.row]
// Downloads the image data for a thumbnail.
photoStore.fetchImageForPhoto(flickrPhoto,thumbnail: true) { (result) -> Void in
// Calls the mainthread to update the UI.
NSOperationQueue.mainQueue().addOperationWithBlock() {
// The indexpath for the photo might have changed between the time the request started and finished, so find the most recent indeaxpath
let photoIndex = self.photoDataSource.flickrPhotos.indexOf(flickrPhoto)!
let photoIndexPath = NSIndexPath(forRow: photoIndex, inSection: 0)
// When the request finishes, only update the cell if it's still visible
if let cell = collectionView.cellForItemAtIndexPath(photoIndexPath) as? PhotoCollectionViewCell {
cell.updateWithImage(flickrPhoto.image)
}
}
}
}
}
//MARK: - Extension UITextFieldDelegate
extension PhotosViewController : UITextFieldDelegate {
func textFieldShouldReturn(textField: UITextField) -> Bool {
// Checks if the textfield is not empty.
if textField.text!.isEmpty {
self.showAlert("S😉rry", message: "No search term detected, please enter a search term.")
return false
}
else {
let activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .Gray)
textField.addSubview(activityIndicator)
activityIndicator.frame = textField.bounds
activityIndicator.startAnimating()
textField.placeholder = TextFieldPlaceHolderText.Searching.rawValue
// Sets the text that the user typed as the value for the searchTerm property.
searchTerm = textField.text!
// Fetches the photos from flickr using the user's search term.
photoStore.fetchPhotosForSearchTerm() {
(photosResult) -> Void in
// Calls the mainthread to update the UI.
NSOperationQueue.mainQueue().addOperationWithBlock() {
switch photosResult {
case let .Success(photos):
// Checks if photos were found using the search term.
if photos.count == 0 {
self.showAlert("S😞rry", message: "No images found matching your search for: \(searchTerm!), please try again.")
}
activityIndicator.removeFromSuperview()
textField.placeholder = TextFieldPlaceHolderText.Search.rawValue
// Sets the result to the data source array.
self.photoDataSource.flickrPhotos = photos
print("Successfully found \(photos.count) recent photos.")
case let .Failure(error):
self.checkForReachability()
activityIndicator.removeFromSuperview()
textField.placeholder = TextFieldPlaceHolderText.Search.rawValue
self.photoDataSource.flickrPhotos.removeAll()
self.showAlert("", message: "Something went wrong, please try again.")
print("Error fetching photo's for search term: \(searchTerm!), error: \(error)")
}
self.collectionView.reloadSections(NSIndexSet(index: 0))
}
}
textField.text = nil
textField.resignFirstResponder()
self.collectionView?.backgroundColor = UIColor.whiteColor()
return true
}
}
}
The detail view controller:
import UIKit
import Social
class PhotoDetailViewController: UIViewController {
// MARK: - Outlets
#IBOutlet var photoTitleLabel: UILabel!
#IBOutlet var photoIDLabel: UILabel!
#IBOutlet var dateTakenLabel: UILabel!
#IBOutlet var imageView: UIImageView!
// MARK: Properties
var flickrPhoto: FlickrPhoto!
var photoStore: PhotoStore!
let formatter = FlickrAPI.dateFormatter
// MARK: - View Setup
override func viewDidLoad() {
super.viewDidLoad()
//Downloads the image data for large image
photoStore.fetchImageForPhoto(flickrPhoto, thumbnail: false) { (result) -> Void in
switch result {
case let .Success(image):
// Calls the mainthread to update the UI.
NSOperationQueue.mainQueue().addOperationWithBlock() {
self.imageView.image = image
}
case let .Failure(error):
print(" Error fetching detail image for photo: \(error)")
}
}
// Formats the date a shorte date that doesn't display the time
formatter.dateStyle = .MediumStyle
formatter.timeStyle = .NoStyle
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
// Checks if the device is connected to the internet.
checkForReachability()
// Configures the UI.
configureView()
}
// MARK: - checkForReachability
func checkForReachability() {
do {
reachability = try Reachability.reachabilityForInternetConnection()
} catch {
print("Unable to create Reachability")
return
}
reachability!.whenReachable = { reachability in
// this is called on a background thread, but UI updates must be on the main thread, like this:
NSOperationQueue.mainQueue().addOperationWithBlock({
if reachability.isReachableViaWiFi() {
print("Reachable via WiFi")
} else {
print("Reachable via Cellular")
}
})
}
reachability!.whenUnreachable = { reachability in
// this is called on a background thread, but UI updates must be on the main thread, like this:
NSOperationQueue.mainQueue().addOperationWithBlock({
print("Not reachable")
self.showAlert("No Internet Connection", message: "Make sure your device is connected to the internet.")
})
}
do {
try reachability!.startNotifier()
} catch {
print("Unable to start notifier")
}
}
// MARK: - configureView
func configureView() {
photoTitleLabel.text = flickrPhoto.title ?? "No title available"
photoIDLabel.text = flickrPhoto.photoID ?? "ID unknown"
dateTakenLabel.text = formatter.stringFromDate(flickrPhoto.dateTaken) ?? " Date unknown"
}
// MARK: - showShareOptions
#IBAction func showShareOptions(sender: AnyObject) {
// Configure an action sheet to show the sharing options.
let actionSheet = UIAlertController(title: "Share this photo", message: "", preferredStyle: UIAlertControllerStyle.ActionSheet)
let tweetAction = UIAlertAction(title: "Share on Twitter", style: UIAlertActionStyle.Default) { (action) -> Void in
// Check if sharing to Twitter is possible.
if SLComposeViewController.isAvailableForServiceType(SLServiceTypeTwitter) {
let twitterComposeVC = SLComposeViewController(forServiceType: SLServiceTypeTwitter)
twitterComposeVC.addImage(self.imageView.image)
self.presentViewController(twitterComposeVC, animated: true, completion: nil)
}
else {
self.showAlert("Flickr Searcher", message: "You are not logged in to your Twitter account.")
}
}
// Configure a new action to share on Facebook.
let facebookPostAction = UIAlertAction(title: "Share on Facebook", style: UIAlertActionStyle.Default) { (action) -> Void in
if SLComposeViewController.isAvailableForServiceType(SLServiceTypeTwitter) {
let facebookComposeVC = SLComposeViewController(forServiceType: SLServiceTypeFacebook)
facebookComposeVC.addImage(self.imageView.image)
self.presentViewController(facebookComposeVC, animated: true, completion: nil)
}
else {
self.showAlert("Flickr Searcher", message: "You are not logged in to your facebook account.")
}
}
// Configure a new action to show the UIActivityViewController
let moreAction = UIAlertAction(title: "More", style: UIAlertActionStyle.Default) { (action) -> Void in
let activityViewController = UIActivityViewController(activityItems: [self.imageView.image!], applicationActivities: nil)
self.presentViewController(activityViewController, animated: true, completion: nil)
}
let dismissAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Destructive) { (action) -> Void in
}
actionSheet.addAction(tweetAction)
actionSheet.addAction(facebookPostAction)
actionSheet.addAction(moreAction)
actionSheet.addAction(dismissAction)
presentViewController(actionSheet, animated: true, completion: nil)
}
// MARK: showAlert
func showAlert(title: String, message: String) {
let alert = UIAlertController(title: title, message: message, preferredStyle: .Alert)
let okAction = UIAlertAction(title: "Ok", style: .Cancel, handler: { (nil) in
self.dismissViewControllerAnimated(true, completion: nil)
})
alert.addAction(okAction)
self.presentViewController(alert, animated: true, completion: nil)
}
}
My data source:
import UIKit
class PhotoDataSource: NSObject, UICollectionViewDataSource {
//MARK: - Properties
// Array to store the Flickr Photos
var flickrPhotos = [FlickrPhoto]()
// An instance of photoStore.
var photoStore = PhotoStore()
// MARK: - numberOfItemsInSection
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return flickrPhotos.count
}
// MARK: - cellForItemAtIndexPath
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let identifier = "FlickrCell"
let cell = collectionView.dequeueReusableCellWithReuseIdentifier(identifier, forIndexPath: indexPath) as! PhotoCollectionViewCell
let photo = flickrPhotos[indexPath.item]
cell.updateWithImage(photo.image)
print(indexPath.item)
// If you get close to the end of the collection, fetch more photo's.
if indexPath.item == flickrPhotos.count - 20 {
print("Detected the end of the collection")
// Fetch the next batch of photos.
photoStore.fetchPhotosForSearchTerm() {
(photosResult) -> Void in
// Calls the mainthread to update the UI.
NSOperationQueue.mainQueue().addOperationWithBlock() {
switch photosResult {
case let .Success(photos):
print("Successfully found \(photos.count) recent photos.")
self.flickrPhotos.appendContentsOf(photos)
case let .Failure(error):
self.flickrPhotos.removeAll()
print("Error fetching more photos for search term \(error)")
}
collectionView.reloadSections(NSIndexSet(index: 0))
}
}
}
return cell
}
}
This is the method that throws the error. But only when navigated to the detail view first. Staying in the collection view the method gets call over and over with no problem:
photoStore.fetchPhotosForSearchTerm() {
(photosResult) -> Void in
// Calls the mainthread to update the UI.
NSOperationQueue.mainQueue().addOperationWithBlock() {
switch photosResult {
case let .Success(photos):
print("Successfully found \(photos.count) recent photos.")
self.flickrPhotos.appendContentsOf(photos)
case let .Failure(error):
self.flickrPhotos.removeAll()
print("Error fetching more photos for search term \(error)")
}
collectionView.reloadSections(NSIndexSet(index: 0))
}
}