CODEWITHSUNDEEP
swiftcocoa-touchrx-swift
Oleksandr Balabanov
Oleksandr Balabanov

Reputation: 639

Mutating of RxSwift Driver value

In my application I have an array of notifications. Notification can be read and unread.

When user clicks on the unread notification I need to change the model and reload data in my table view.

In my ViewModel I have output stream:

let notifications: Driver<[Notification]>

And aslo I have an input stream with notification click:

let touchSingleNotificationIntent = PublishSubject<Notification>()

When I do something like this I get the error that it's let constant and I cannot mutate it.

touchSingleNotificationIntent
        .filter { !$0.isRead }
        .do(onNext: { notification in
            notification.isRead = true // I need to change state of the model immediately after user iteration
        })
        .map { $0.notificationID }
        .flatMap(markNotificationAsRead) // http request which doesn't reply with current notification model status
        .subscribe()
        .disposed(by: bag)

Do you have any ideas how to make it mutable? Thanks.

Upvotes: 0

Views: 5683

Answers (2)

Shai Mishali
Shai Mishali

Reputation: 9382

Streams aren't Mutable at all (this is the same for Observable, Driver, and any other traits). They are "Read only", you read values off the stream over time.

In general, the conception Observables has a "value" is a bit wrong since Observables represent a value over time, and not just a single value.

What you would want to do is "take into account" your PublishSubject when building out your driver.

Something like this would work: 

notifications = Observable
    .combineLatest(touchedNotification, readNotification, otherEvent) { ($0, $1, $2) }
    .map { ... map the three values into whatever makes sense for you }
    .asDriver(onErrorJustReturn: ... fallback value ... }

Again, the most important fact to remember - You do not actually mutate streams, you only combine them, transform them, etc, to create a new stream that suits your needs.

Hope this helps you!

Upvotes: 1

Maxim Volgin
Maxim Volgin

Reputation: 4077

Parameters of onNext are let by default. You can define a new one with var, i.e. 'var newNotification = notification' and then return it after modifying.

Upvotes: 0

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