make dynamic UIbutton appear and dissapear based on number of items in table view - swift

Question

I'm currently trying to make a dynamic UIbutton appear and disappear based on number of items loaded into a table view, fetched from a backend url. I want to button to appear if there's 12 or more items loaded into the table view and not appear if there's less than 12. Any ideas on the best way to handle this?
import UIKit
import RxSwift
import RxCocoa
public class AllProvidersPickerViewController: InputableTableViewController, ViewModelHolder {
#IBOutlet private(set) weak var searchBar: UISearchBar!
#IBOutlet weak var dontSeeProviderButton: UIButton!
var viewModel: AllProvidersPickerViewModel! = nil
private let bag = DisposeBag()
override public func viewDidLoad() {
super.viewDidLoad()
setupRx()
}
private func setupRx() {
viewModel.shownProviders
.bind(to: tableView.rx.items(cellIdentifier: "ProviderCell")) { _, mvpd, cell in
cell.textLabel?.text = mvpd.displayName
}
.addDisposableTo(bag)
tableView
.rx
.modelSelected(MVPD.self)
.bind(to: viewModel.selectedProvider)
.addDisposableTo(bag)
searchBar
.rx.text
.orEmpty
.bind(to: viewModel.searchQuery)
.addDisposableTo(bag)
dontSeeProviderButton
.rx.tap
.bind(to: viewModel.tappedDontSeeProvider)
.addDisposableTo(bag)
}
}
private extension MVPD {
var displayName: String {
return self.names.first ?? ""
}
}

Answer 1

XFreire's answers are fine, or you could do:
viewModel.shownProviders
.map { $0.count < 12 }
.bind(to: dontSeeProviderButton.rx.isHidden)
.disposed(by: bag)
Make sure shownProviders can handle being subscribed to without having to re-send any network requests or whatever. You might need shareReplayLatestWhileConnected() for that.
I have been asked to explain this code... I will do so by breaking it down...
let shownProviders = viewModel.shownProviders
At this point, I know that shownProviders is an array. I don't know much about the type that the array contains because that info wasn't in the question, but I don't need to know
let shownProviders = viewModel.shownProviders
let shouldHideButton = shownProviders.map { $0.count < 12 }
In the above line, I know that $0 is an array and I know that the button should hide if there are fewer than 12 items in the array. $0.count < 12 returns a Bool. map will transform the shownProviders Observable into whatever the block returns, so I know that shouldHideButton is an Observable<Bool>.
let shownProviders = viewModel.shownProviders
let shouldHideButton = shownProviders.map { $0.count < 12 }
let disposable = shouldHideButton.bind(to: dontSeeProviderButton.rx.isHidden)
The above line of code binds the result of shouldHideButton to the isHidden property of the button. It returns a disposable.
let shownProviders = viewModel.shownProviders
let shouldHideButton = shownProviders.map { $0.count < 12 }
let disposable = shouldHideButton.bind(to: dontSeeProviderButton.rx.isHidden)
disposable.disposed(by: bag)
This last line ensures that the binding will be broken when the view controller goes out of scope.

Answer 2

Simplest way:
viewModel.shownProviders
.subscribe(onNext: { [weak self] items in
if items.count < 12 {
self?.viewAllProvidersButton.isHidden = true
}
else {
self?.viewAllProvidersButton.isHidden = false
}
})
.addDisposableTo(bag)
Other way could be to create a property buttonVisibilityObserver of type AnyObserver and bind it to viewModel.shownProviders. Something like this (not tested):
var buttonVisibilityObserver: AnyObserver<[ItemsType]> {
return UIBindingObserver(UIElement: viewAllProvidersButton) { button, items in
button.isHidden = items.count < 12 ? true : false
}.asObserver()
}
And then in your setupRx():
viewModel.shownProviders
.bind(to: buttonVisibilityObserver)
.addDisposableTo(bag)