Using zip operator in RxSwift after creating an array of observables

Question

I have a newBid object, that contains some data and images array. I want to upload all images and data to the server and zip those upload observables. If I create separate drivers for data, image1 and image2, I succeed.

But what I want to really do is to not hardcode images since array may contain from 0 to 10 images. I want to create observables array programmatically and zip them.

let dataSaved = saveTaps.withLatestFrom(newBid)
    .flatMapLatest { bid in
        return CustomerManager.shared.bidCreate(bid: bid)
            .trackActivity(activityIndicator)
            .asDriver(onErrorJustReturn: false)
}

let photoSaved0 = saveTaps.withLatestFrom(newBid)
    .flatMapLatest { bid in
        return CustomerManager.shared.bidUploadFile(image: bid.images[0])
            .trackActivity(activityIndicator)
            .asDriver(onErrorJustReturn: false)
}

let photoSaved1 = saveTaps.withLatestFrom(newBid)
    .flatMapLatest { bid in
        return CustomerManager.shared.bidUploadFile(image: bid.images[1])
            .trackActivity(activityIndicator)
            .asDriver(onErrorJustReturn: false)
}

saveCompleted = Driver.zip(dataSaved, photoSaved0, photoSaved1){ return $0 && $1 && $2 }

/*
// 0. Getting array of images from newBid
let images = newBid.map { bid in
    return bid.images
}

// 1. Creating array of upload drivers from array of images
let imageUploads = images.map { (images: [UIImage]) -> [Driver<Bool>] in
    var temp = [Driver<Bool>]()
    return temp
}

// 2. Zipping array of upload drivers to photoSaved driver
photoSaved = Driver
    .zip(imageUploads) // wait for all image requests to finish
    .subscribe(onNext: { results in
        // here you have every single image in the 'images' array
        results.forEach { print($0) }
    })
    .disposed(by: disposeBag)*/

In the commented section if I try to zip imageUploads, I get error:

Argument type 'SharedSequence<DriverSharingStrategy, [SharedSequence<DriverSharingStrategy, Bool>]>' does not conform to expected type 'Collection'

Daniel T. · Accepted Answer · 2018-08-19T17:48:45.673

2

How about something like this?

let saves = saveTaps.withLatestFrom(newBid)
    .flatMapLatest { (bid: Bid) -> Observable<[Bool]> in
        let dataSaved = CustomerManager.shared.bidCreate(bid: bid)
            .catchErrorJustReturn(false)

        let photosSaved = bid.images.map {
            CustomerManager.shared.bidUploadFile(image: $0, bidID: bid.id)
                .catchErrorJustReturn(false)
        }

        return Observable.zip([dataSaved] + photosSaved)
            .trackActivity(activityIndicator)
    }
    .asDriver(onErrorJustReturn: []) // remove this line if you want an Observable<[Bool]>.

edited Aug 19 '18 at 17:48

answered Aug 16 '18 at 11:35

Daniel T.

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Thanks, I will try. – Denis Kutlubaev Aug 16 '18 at 15:38
As an FYI. The `zip` operator doesn't upload the images one at a time. It will start all the uploads at the same time and report back when they are all complete. – Daniel T. Aug 16 '18 at 18:35
I have an error with this: Cannot convert value of type '(Bid) -> Observable<[Bool]>' to expected argument type '(_) -> SharedSequence<_, _>' – Denis Kutlubaev Aug 19 '18 at 13:20
What do your CustomerManager functions return? I was assuming they returned Observable. – Daniel T. Aug 19 '18 at 13:24
Yes. It returns Observable – Denis Kutlubaev Aug 19 '18 at 14:33
Look at my final solution below. I made it using your ideas. But I changed a little bit my initial code by first adding bid object on server and getting it's ID, then uploading images for it. – Denis Kutlubaev Aug 19 '18 at 14:35
A `SharedSequence` is a Driver. If you want an `Observable<[Bool]>` just remove the `.asDriver...` line. – Daniel T. Aug 19 '18 at 17:45

Denis Kutlubaev · Answer 2 · 2018-08-19T14:34:32.163

Final solution

let bidID: Driver<Int> = saveTaps.withLatestFrom(newBid)
    .flatMapLatest { bid in
        return CustomerManager.shared.bidCreate(bid: bid)
            .trackActivity(activityIndicator)
            .asDriver(onErrorJustReturn: 0)
}

saveCompleted = Driver.combineLatest(bidID, newBid) { bidID, newBid in
    newBid.uploadedImages.map {
        CustomerManager.shared.bidUploadFile(image: $0, bidID: bidID).asDriver(onErrorJustReturn: false)
    }
    }.flatMap { imageUploads in
        return Driver.zip(imageUploads).trackActivity(activityIndicator).asDriver(onErrorJustReturn: [])
    }.map{ (results:[Bool]) -> Bool in
        return !results.contains(false)
}

It is a combined version of this which is equivalent:

let imageUploads: Driver<[Driver<Bool>]> = Driver.combineLatest(bidID, newBid) { bidID, newBid in
    newBid.uploadedImages.map {
        CustomerManager.shared.bidUploadFile(image: $0, bidID: bidID).asDriver(onErrorJustReturn: false)
    }
}

let photosSaved: Driver<[Bool]> = imageUploads.flatMap { imageUploads in
    return Driver.zip(imageUploads).trackActivity(activityIndicator).asDriver(onErrorJustReturn: [])
}

saveCompleted = photosSaved.map{ (results:[Bool]) -> Bool in
    return !results.contains(false)
}

Using zip operator in RxSwift after creating an array of observables

2 Answers2