Rx: combineLatest vs withLatestFrom (and zip)

Martin Konicek
Jan 17, 2018 · 3 min read

combineLatest

disposables += Observable.combineLatest(        view.onNameChanged(), view.onEmailChanged(), ::AccountInfo)        .subscribe { accountInfo ->               view.setNextStepButtonEnabled(accountInfo.isValid())        }

withLatestFrom

disposables += view.onNameFocusChanged()      // When focus changes          .withLatestFrom(view.onNameChanged()) // Grab the name          .subscribe { (focus, name) ->            val hasLostFocus = !focus            if (hasLostFocus && !isValidName(name)) {              view.showInvalidName()            } else {              view.clearNameError()            }          }

What about the zip operator?

When each Observable returns at most one value: zip and combineLatest will do the same thing.

Martin Konicek

Written by

Software Engineer based in London

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