How to know completion of map on a Single in ViewModel?

Question

I have a function in ViewModel which is getting some data from network file as Single. In viewModel I am using map to convert it to different model and return it to ViewController. Once this map/conversion is complete I want to update a BehaviorRelay object in ViewModel to tell its subscribers that downloading is complete. I am not able to update this BehaviorRelay object.

I tried to add some code in the function but I get error in return statement.

var showLoading = BehaviorRelay<Bool>(value: true)
func getPropertyList(city cityID: String) -> Single<[Property]> {
        return propertyListApi.getPropertyList(city: cityID).map({ [weak self] propertInfo -> [Property] in
            propertInfo.map({
                return Property(name: $0.name, type: "Property Type: " + $0.type, lowestPricePerNight: "", overallRatingPercentage: "Rating: " + String($0.overallRating.overall ?? 0), image: self?.getImageURL(images: $0.images))
            })
        })
    }

I want to update showLoading in getPropertyList function to let ViewController know that loading is complete.

Answer 1

You can do this by subscribing your showLoading to the result... Also note that showLoading should be a let, not a var.

let showLoading = BehaviorRelay<Bool>(value: true)
func getPropertyList(city cityID: String) -> Single<[Property]> {
    let result = propertyListApi.getPropertyList(city: cityID).map({ [weak self] propertyInfo -> [Property] in
        propertyInfo.map({
            return Property(name: $0.name, type: "Property Type: " + $0.type, lowestPricePerNight: "", overallRatingPercentage: "Rating: " + String($0.overallRating.overall ?? 0), image: self?.getImageURL(images: $0.images))
        })
    })

    result
        .asObservable()              // convert your Single to something that can emit multiple values.
        .map { _ in false }          // when the request emits a value, emit `false`.
        .startWith(true)             // when the request starts, emit `true`.
        .catchErrorJustReturn(false) // if the request fails, emit `false`.
        .bind(to: showLoading)       // listen to the emissions above and set yourself accordingly.
        .disposed(by: disposeBag)    // if self is deleted, cancel the subscription.

    return result
}