How to check if an observable is empty in RXSwift?

Question

i have initialized an empty observable like this:

var subCategories = Observable<[String]>.empty()

How can i check if the observable is empty or not? I would like to show a "empty view" to the user if the observable is empty else show the data in tableview.

Empty Observable refers to an Observable emit a single `onComplete`. The use-case you described should be implemented with an Observable which emits `[String]` with length from 0 to n. — duan, Sep 18 '19 at 13:09

Behrad Kazemi · Answer 1 · 2019-09-18T14:25:31.697

1

create a bool Observable to show/hide your emptyView:

let hideEmptyView = subCategories.map{!$0.isEmpty}

then bind this hideEmptyView Bool Observable to yourEmptyView.rx.isHidden

edited Sep 18 '19 at 14:25

answered Sep 18 '19 at 14:19

Behrad Kazemi

302
1
10

score 0 · Answer 2 · answered Jan 07 '22 at 12:39

You have to use filter on the Observable :

viewModel.filteredUsers.asObservable()
        .filter({ [weak self] array in
            guard let self = self else {return true}
            
            if array.isEmpty {
                self.emptyListContainer.alpha = 1
                self.tableView.alpha = 0
            } else {
                self.emptyListContainer.alpha = 0
                self.tableView.alpha = 1
                
            }
            return true
        })
        .bind(to: tableView.rx.items(cellIdentifier: "ContactsTableViewCell", cellType: ContactsTableViewCell.self)) { (row, user, cell) in
        cell.titleLbl.text = user.name
    }
    .disposed(by: disposeBag)

score -1 · Answer 3 · answered Aug 14 '20 at 08:11

use a BehaviourRelay other than Observable.

import RxCocoa
import RxSwift

var subCategories = BehaviorRelay<[String]>(value: [])
let emptyView = UIStackView()

func addObservers() {
    subCategories.asObservable().subscribe { _ in
        self.emptyView.isHidden = !self.subCategories.value.isEmpty
    }.disposed(by: DisposeBag())
}

How to check if an observable is empty in RXSwift?

3 Answers3