iosswiftzipsystem.reactivetake

How do I take the last ten elements from an rx observable?


I have an Observable that combine three other Observables then emit a single array. From this merged array I would like to take the last 10 objects. But I think I take the last ten arrays instead. Tried using compactMap first but that didn't do the trick. It's still returned as an array

return Observable.combineLatest(breakfast, dessert, cookies) { $0 + $1 + $2 }
    .compactMap { $0 }.takeLast(10)
    .do(onNext: { [weak self] value in
        self?.content.accept(value.compactMap {
            NewRecipesCollectionViewCellViewModel(recipe: $0)})
        })

Solution

  • With this approach you get back the elements one by one:

        let breakfast = Observable.just(["egg", "milk"])
        let dessert = Observable.just(["ice cream", "chocolate"])
        let cookies = Observable.just(["cookie1", "cookie2"])
    
        Observable.combineLatest(breakfast, dessert, cookies)
            .map { $0 + $1 + $2 }
            .do(onNext: { foods in
                let lastTenFood = foods.suffix(10) // returns the last 10 elements from the array
                for food in lastTenFood {
                    print("Food: \(food)")
                }
            })
            .subscribe()
            .disposed(by: disposeBag)