When I'm trying to update my datasource (which is custom in a separate class) from a closure inside the respective ViewController it won't work.
So this is the code I'm calling to update the datasource with
extension YelpSearchController: UISearchResultsUpdating {
func updateSearchResults(for searchController: UISearchController) {
guard let searchTerm = searchController.searchBar.text else {
return
}
let yelpCoordinate = YLPCoordinate(latitude: 37.785834000000001, longitude: -122.406417)
let yelpClient = YLPClient.init(apiKey: appSecret)
yelpClient.search(with: yelpCoordinate, term: searchTerm , limit: 30, offset: 1, sort: YLPSortType.distance) { [weak self] result, error in
guard let results = result else { return }
let businesses = results.businesses
self?.dataSource.update(with: businesses)
}
}
}
And this is the function that is just updating my data variable inside the datasource class, as follows:
private var data = [YLPBusiness]()
func update(with data: [YLPBusiness]) {
self.data = data
}
The problem is when I call the delegate methods, as required as a datasource, they are initially called but when they are the data variable has still not been updated, so the data is nil.
If I for example try and print the data.count inside of the update func I get a result. But inside of any of the delegate methods (cellForRowAt, numberOfRowsInSection), it's all nil. So all the methods concerning and using the data variable except the update function they are not getting the data since the view is loading but the data comes after when the user inputs in the search field.
So the question is how do I get the data accessible to the delegate methods?
Forgot to update the datasource after I've received the data from inside the closure.
yelpClient.search(with: yelpCoordinate, term: searchTerm , limit: 30, offset: 1, sort: YLPSortType.distance) { [weak self] result, error in
guard let results = result else { return }
let businesses = results.businesses
self?.dataSource.update(with: businesses)
DispatchQueue.main.async {. // added this
self?.tableView.reloadData()
}
Big thanks to DonMag for the correct answer.
Related
I'm currently attempting to pull a series of items from my database, and append them into an array stored within a variable.
This works successfully - and once the viewDidLoad executes.
I then want to call a function which iterates through this array, and for each element in it, pull out a balance and add it to a global variable.
I can do this by calling the function inside my initial database call, and wrapping it in DispatchQueue, however - it's duplicating, and actually doubling the value, almost like the add function is being called twice.
But I can't see where this is happening, or why. My understanding is that this database call only occurs once, but it seems like the function is getting called twice.
Particularly, my problem is happening like follows:
totalBalance is equal to 0 while the database call resolves
database call finds two entries, saves them to accounts variable
calculateBalance finds first balance of 2, second balance of 3 and adds together, updating totalBalance variable to 5
calculateBalance gets called again, adding 2 and 3 to totalBalance and equalling 10
totalBalance should equal 5, but it gets 2 + 3 twice, so ends up as being 10.
Here's my code:
class DashboardViewController: UIViewController {
let db = Firestore.firestore()
var accounts: [Account] = []
var totalBalance: Int = 0
#IBOutlet weak var tableView: UITableView!
#IBOutlet weak var balanceLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
fetchAccounts()
}
func fetchAccounts() {
db.collection("accounts")
.getDocuments { (QuerySnapshot, error) in
if let err = error {
print("Error getting documents: \(err)")
} else {
if let snapshotDocuments = QuerySnapshot?.documents {
for doc in snapshotDocuments {
let data = doc.data()
if let balance = data["accountBalance"] as? String {
let newAccount = Account(
accountBalance: balance,
)
self.accounts.append(newAccount)
}
DispatchQueue.main.async {
self.calculateBalance()
self.tableView.reloadData()
}
}
}
}
}
}
func calculateBalance() {
for cash in accounts {
totalBalance += Int(cash.accountBalance)!
}
DispatchQueue.main.async {
self.balanceLabel.text = "Overall balance - -£\(self.totalBalance)"
}
}
}
Any feedback here would be really appreciated - been scratching my head but think someone coming in from the outside will be able to spot what my problem is.
If I'm reading this correctly, you're calling the calculateBalance method in a loop, if you had 5 accounts in snapshotDocuments the method would get called 5 times:
for doc in snapshotDocuments {
let data = doc.data()
if let balance = data["accountBalance"] as? String {
let newAccount = Account(
accountBalance: balance,
)
self.accounts.append(newAccount)
}
//This will get called multiple times
//DispatchQueue.main.async {
// self.calculateBalance()
// self.tableView.reloadData()
//}
}
//This will get called only once
DispatchQueue.main.async {
self.calculateBalance()
self.tableView.reloadData()
}
I have the following MVVM-C + RxSwift code.
The problem is that the TableView is not receiving any signals. When I
debug the results I can see that the API call is returning what it should, the objects array is populated with objects but the tableview does not show any results. Here is the console output:
2018-11-13 16:12:08.107: searchText -> Event next(qwerty)
Search something: qwerty
2018-11-13 16:12:08.324: viewModel.data -> Event next([])
Could it be the tableview itself? Maybe wrong custom cell setup?
ViewController.swift:
tableView = UITableView(frame: self.view.frame)
tableView.delegate = nil
tableView.dataSource = nil
tableView.register(SearchResultCell.self, forCellReuseIdentifier: "SearchResultCell")
viewModel.data
.debug("viewModel.data", trimOutput: false)
.drive(tableView.rx.items(cellIdentifier: "SearchResultCell")) { row, object, cell in
cell.name.text = object.name
cell.something.text = object.something
}
.disposed(by: disposeBag)
ViewModel.swift:
let disposeBag = DisposeBag()
var searchText = BehaviorRelay(value: "something to search for")
lazy var data: Driver<[Object]> = {
return self.searchText.asObservable()
.debug("searchText", trimOutput: false)
.throttle(0.3, scheduler: MainScheduler.instance)
.distinctUntilChanged()
.flatMapLatest(searchSomething)
.asDriver(onErrorJustReturn: [])
}()
func searchSomething(query: String) -> Observable<[Object]> {
print("Search something: \(query)")
let provider = MoyaProvider<APIService>()
var objects = [Object]()
provider.rx.request(.search(query: query)).subscribe { event in
switch event {
case let .success(response):
do {
let responseJSON: NSDictionary = try (response.mapJSON() as? NSDictionary)!
objects = self.parse(json: responseJSON["results"] as Any)
} catch(let error) {
print(error)
}
break
case let .error(error):
print(error)
break
}
}
.disposed(by: disposeBag)
let result: Observable<[Object]> = Observable.from(optional: objects)
return result
}
When using flatMap, you do not want to create nested subscriptions. You will create an Observable that returns the expected result, and flatMap will take care of subscribing to it. In the current state of things, searchSomething will always return an empty array, as Observable.from(optional: objects) will be called before the request has a chance to complete.
Since version 10.0 of Moya, provider will cancel the requests it created when deallocated. Here, it will be deallocated when execution exits searchSomething, hence the network request won't have time to finish. Moving provider's declaration to the view model's level solves this issue.
Here's searchSomething(query: String) -> Observable<[Object]> rewritten.
let provider = MoyaProvider<APIService>()
func searchSomething(query: String) -> Observable<[Object]> {
print("Search something: \(query)")
return provider.rx.request(.search(query: query)).map { (response) -> [Object] in
let responseJSON: NSDictionary = try (response.mapJSON() as? NSDictionary)!
return self.parse(json: responseJSON["results"] as Any)
}
}
Instead of doing the transformation in subscribe, it's done in map, which will be called for every next event, being passed the value associated with the event.
I am trying to get an array of temperatures in a given time period from an API in JSON format. I was able to retrieve the array through a completion handler but I can't save it to another variable outside the function call (one that uses completion handler). Here is my code. Please see the commented area.
class WeatherGetter {
func getWeather(_ zip: String, startdate: String, enddate: String, completion: #escaping (([[Double]]) -> Void)) {
// This is a pretty simple networking task, so the shared session will do.
let session = URLSession.shared
let string = "api address"
let url = URL(string: string)
var weatherRequestURL = URLRequest(url:url! as URL)
weatherRequestURL.httpMethod = "GET"
// The data task retrieves the data.
let dataTask = session.dataTask(with: weatherRequestURL) {
(data, response, error) -> Void in
if let error = error {
// Case 1: Error
// We got some kind of error while trying to get data from the server.
print("Error:\n\(error)")
}
else {
// Case 2: Success
// We got a response from the server!
do {
var temps = [Double]()
var winds = [Double]()
let weather = try JSON(data: data!)
let conditions1 = weather["data"]
let conditions2 = conditions1["weather"]
let count = conditions2.count
for i in 0...count-1 {
let conditions3 = conditions2[i]
let conditions4 = conditions3["hourly"]
let count2 = conditions4.count
for j in 0...count2-1 {
let conditions5 = conditions4[j]
let tempF = conditions5["tempF"].doubleValue
let windspeed = conditions5["windspeedKmph"].doubleValue
temps.append(tempF)
winds.append(windspeed)
}
}
completion([temps, winds])
}
catch let jsonError as NSError {
// An error occurred while trying to convert the data into a Swift dictionary.
print("JSON error description: \(jsonError.description)")
}
}
}
// The data task is set up...launch it!
dataTask.resume()
}
}
I am calling this method from my view controller class. Here is the code.
override func viewDidLoad() {
super.viewDidLoad()
let weather = WeatherGetter()
weather.getWeather("13323", startdate: "2016-10-01", enddate: "2017-04-30") { (weatherhandler: [[Double]]) in
//It prints out the correct array here
print(weatherhandler[0])
weatherData = weatherhandler[0]
}
//Here it prints out an empty array
print(weatherData)
}
The issue is that API takes some time to return the data, when the data is return the "Completion Listener" is called and it goes inside the "getWeather" method implementation, where it prints the data of array. But when your outside print method is called the API hasn't returned the data yet. So it shows empty array. If you will try to print the data form "weatherData" object after sometime it will work.
The best way I can suggest you is to update your UI with the data inside the "getWeather" method implementation like this:
override func viewDidLoad() {
super.viewDidLoad()
let weather = WeatherGetter()
weather.getWeather("13323", startdate: "2016-10-01", enddate: "2017-04-30") { (weatherhandler: [[Double]]) in
//It prints out the correct array here
print(weatherhandler[0])
weatherData = weatherhandler[0]
// Update your UI here.
}
//Here it prints out an empty array
print(weatherData)
}
It isn't an error, when your controller get loaded the array is still empty because your getWeather is still doing its thing (meaning accessing the api, decode the json) when it finishes the callback will have data to return to your controller.
For example if you were using a tableView, you will have reloadData() to refresh the UI, after you assign data to weatherData
Or you could place a property Observer as you declaring your weatherData property.
var weatherData:[Double]? = nil {
didSet {
guard let data = weatherData else { return }
// now you could do soemthing with the data, to populate your UI
}
}
now after the data is assigned to wheaterData, didSet will be called.
Hope that helps, and also place your jsonParsing logic into a `struct :)
I have this Firebase data:
I want to query the posts data through pagination. Currently my code is converting this JS code to Swift code
let postsRef = self.rootDatabaseReference.child("development/posts")
postsRef.queryOrderedByChild("createdAt").queryStartingAtValue((page - 1) * count).queryLimitedToFirst(UInt(count)).observeSingleEventOfType(.Value, withBlock: { snapshot in
....
})
When accessing, this data page: 1, count: 1. I can get the data for "posts.a" but when I try to access page: 2, count: 1 the returns is still "posts.a"
What am I missing here?
Assuming that you are or will be using childByAutoId() when pushing data to Firebase, you can use queryOrderedByKey() to order your data chronologically. Doc here.
The unique key is based on a timestamp, so list items will automatically be ordered chronologically.
To start on a specific key, you will have to append your query with queryStartingAtValue(_:).
Sample usage:
var count = numberOfItemsPerPage
var query ref.queryOrderedByKey()
if startKey != nil {
query = query.queryStartingAtValue(startKey)
count += 1
}
query.queryLimitedToFirst(UInt(count)).observeSingleEventOfType(.Value, withBlock: { snapshot in
guard var children = snapshot.children.allObjects as? [FIRDataSnapshot] else {
// Handle error
return
}
if startKey != nil && !children.isEmpty {
children.removeFirst()
}
// Do something with children
})
I know I'm a bit late and there's a nice answer by timominous, but I'd like to share the way I've solved this. This is a full example, it isn't only about pagination. This example is in Swift 4 and I've used a nice library named CodableFirebase (you can find it here) to decode the Firebase snapshot values.
Besides those things, remember to use childByAutoId when creating a post and storing that key in postId(or your variable). So, we can use it later on.
Now, the model looks like so...
class FeedsModel: Decodable {
var postId: String!
var authorId: String! //The author of the post
var timestamp: Double = 0.0 //We'll use it sort the posts.
//And other properties like 'likesCount', 'postDescription'...
}
We're going to get the posts in the recent first fashion using this function
class func getFeedsWith(lastKey: String?, completion: #escaping ((Bool, [FeedsModel]?) -> Void)) {
let feedsReference = Database.database().reference().child("YOUR FEEDS' NODE")
let query = (lastKey != nil) ? feedsReference.queryOrderedByKey().queryLimited(toLast: "YOUR NUMBER OF FEEDS PER PAGE" + 1).queryEnding(atValue: lastKey): feedsReference.queryOrderedByKey().queryLimited(toLast: "YOUR NUMBER OF FEEDS PER PAGE")
//Last key would be nil initially(for the first page).
query.observeSingleEvent(of: .value) { (snapshot) in
guard snapshot.exists(), let value = snapshot.value else {
completion(false, nil)
return
}
do {
let model = try FirebaseDecoder().decode([String: FeedsModel].self, from: value)
//We get the feeds in ['childAddedByAutoId key': model] manner. CodableFirebase decodes the data and we get our models populated.
var feeds = model.map { $0.value }
//Leaving the keys aside to get the array [FeedsModel]
feeds.sort(by: { (P, Q) -> Bool in P.timestamp > Q.timestamp })
//Sorting the values based on the timestamp, following recent first fashion. It is required because we may have lost the chronological order in the last steps.
if lastKey != nil { feeds = Array(feeds.dropFirst()) }
//Need to remove the first element(Only when the lastKey was not nil) because, it would be the same as the last one in the previous page.
completion(true, feeds)
//We get our data sorted and ready here.
} catch let error {
print("Error occured while decoding - \(error.localizedDescription)")
completion(false, nil)
}
}
}
Now, in our viewController, for the initial load, the function calls go like this in viewDidLoad. And the next pages are fetched when the tableView will display cells...
class FeedsViewController: UIViewController {
//MARK: - Properties
#IBOutlet weak var feedsTableView: UITableView!
var dataArray = [FeedsModel]()
var isFetching = Bool()
var previousKey = String()
var hasFetchedLastPage = Bool()
//MARK: - ViewController LifeCycle
override func viewDidLoad() {
super.viewDidLoad()
//Any other stuffs..
self.getFeedsWith(lastKey: nil) //Initial load.
}
//....
func getFeedsWith(lastKey: String?) {
guard !self.isFetching else {
self.previousKey = ""
return
}
self.isFetching = true
FeedsModel.getFeedsWith(lastKey: lastKey) { (status, data) in
self.isFetching = false
guard status, let feeds = data else {
//Handle errors
return
}
if self.dataArray.isEmpty { //It'd be, when it's the first time.
self.dataArray = feeds
self.feedsTableView.reloadSections(IndexSet(integer: 0), with: .fade)
} else {
self.hasFetchedLastPage = feeds.count < "YOUR FEEDS PER PAGE"
//To make sure if we've fetched the last page and we're in no need to call this function anymore.
self.dataArray += feeds
//Appending the next page's feed. As we're getting the feeds in the recent first manner.
self.feedsTableView.reloadData()
}
}
}
//MARK: - TableView Delegate & DataSource
//....
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
if self.dataArray.count - 1 == indexPath.row && !self.hasFetchedLastPage {
let lastKey = self.dataArray[indexPath.row].postId
guard lastKey != self.previousKey else { return }
//Getting the feeds with last element's postId. (postId would be the same as a specific node in YourDatabase/Feeds).
self.getFeedsWith(lastKey: lastKey)
self.previousKey = lastKey ?? ""
}
//....
}
I'm building an app with MVC Model.
I use lazy load technical to fill up a variable. (Model)
And this variable is being by one UIViewController (Controller)
But i don't know how to reload or trigger the view controller when the model action is finished. Here is my code
Model (lazy load data)
class func allQuotes() -> [IndexQuotes]
{
var quotes = [IndexQuotes]()
Alamofire.request(.GET, api_indexquotes).responseJSON { response in
if response.result.isSuccess && response.result.value != nil {
for i in (response.result.value as! [AnyObject]) {
let photo = IndexQuotes(dictionary: i as! NSDictionary)
quotes.append(photo)
}
}
}
return quotes
}
And the part of view controller
class Index:
UIViewController,UICollectionViewDelegate,UICollectionViewDataSource {
var quotes = IndexQuotes.allQuotes()
var collectionView:UICollectionView!
override func viewDidLoad() {
This is really serious question, i'm confusing what technic will be used to full fill my purpose?
Since Alamofire works asynchronously you need a completion block to return the data after being received
class func allQuotes(completion: ([IndexQuotes]) -> Void)
{
var quotes = [IndexQuotes]()
Alamofire.request(.GET, api_indexquotes).responseJSON { response in
if response.result.isSuccess && response.result.value != nil {
for photoDict in (response.result.value as! [NSDictionary]) {
let photo = IndexQuotes(dictionary: photoDict)
quotes.append(photo)
}
}
completion(quotes)
}
}
Or a bit "Swiftier"
... {
let allPhotos = response.result.value as! [NSDictionary]
quotes = allPhotos.map {IndexQuotes(dictionary: $0)}
}
I'd recommend also to use native Swift collection types rather than NSArray and NSDictionary
In viewDidLoad in your view controller call allQuotes and reload the table view in the completion block on the main thread.
The indexQuotes property starting with a lowercase letter is assumed to be the data source array of the table view
var indexQuotes = [IndexQuotes]()
override func viewDidLoad() {
super.viewDidLoad()
IndexQuotes.allQuotes { (quotes) in
self.indexQuotes = quotes
dispatch_async(dispatch_get_main_queue()) {
self.tableView.reloadData()
}
}
}
First of all call the function from inside the viewdidLoad. Secondly use blocks or delegation to pass the control back to ViewController. I would prefer the blocks approch. You can have completion and failure blocks. In completions block you can reload the views and on failure you can use alertcontroller or do nothing.
You can see AFNetworking as an example for blocks.
It's async action, just use a callback here:
class func allQuotes(callback: () -> Void) -> [IndexQuotes]
{
var quotes = [IndexQuotes]()
Alamofire.request(.GET, api_indexquotes).responseJSON { response in
if response.result.isSuccess && response.result.value != nil {
for i in (response.result.value as! [AnyObject]) {
let photo = IndexQuotes(dictionary: i as! NSDictionary)
quotes.append(photo)
}
}
callback()
}
return quotes
}
In your UIViewController:
var quotes = IndexQuotes.allQuotes() {
self.update()
}
var collectionView:UICollectionView!
override func viewDidLoad() {
update()
}
private func update() {
// Update collection view or whatever.
}
Actually, I strongly don't recommend to use class functions in this case (and many other cases too), it's not scalable and difficult to maintain after some time.