PromiseKit go back one step

Question

I have a series of UIViewControllers (popups) in my app that I use to gather information from the end user. I managed to chain them with promises like this:

firstly {
        return showFirstPopup()
    }
    .then { info1 -> Promise<Info2> in
        dismissFirstPopup()
        //Do sth with info1...
        return showSecondPopup()
    }
    .then { info2 -> Promise<Info3> in
        dismissSecondPopup()
        //Do sth with info2...
        return showThirdPopup()
    }
    .then { info3 -> Promise<Info4> in
        dismissThirdPopup()
        //Do sth with info3...
        return showForthPopup()
    }
    ...
    .catch { error in
        //Handle any error or cancellation...
     }

If, for example, the user presses back in the third popup I need to go back to the previous "then" and not cancel the whole flow.

Basically I need to be able to go back one step, let the user edit the data, then continue the flow.

Is there a way to do this with PromiseKit?

Answer 1

This is what I ended up using. Hope this helps someone else out there as well.

func myFunc(info: Info) -> Promise<()>
{
    return Promise { fulfill, reject in

        let firstPromise = shouldShowFirstPopup ? showFirstPopup() : Promise(value: info.info1)

        firstPromise
        .then { info1 -> Promise<Info2> in
            info.info1 = info1

            if (info.shouldShowSecondPopup) {
                return showSecondPopup()
            }

            return Promise(value: info.info2)
        }
        .then { info2 -> Promise<Info3> in
            info.info2 = info2
            info.shouldShowSecondPopup = false

            if (info.shouldShowThirdPopup) {
                return showThirdPopup()
            }

            return Promise(value: info.info3)
        }
        .then { info3 -> Promise<()> in
            info.info3 = info3
            info.shouldShowThirdPopup = false

            return processEverything()
        }
        .then { _ -> () in
            fulfill(())
        }
        .catch { error in
            switch error {
                case MyErrors.backPressed(let popupType):
                    switch popupType {
                        case .firstPopup:
                        reject(MyErrors.userCanceled)
                        return

                        case .secondPopup:
                        info.shouldShowFirstPopup = true
                        info.shouldShowSecondPopup = true

                        case .thirdPopup:
                        info.shouldShowSecondPopup = true
                        info.shouldShowThirdPopup = true

                        default:
                        reject(MyErrors.defaultError(message: "Not implemented case exception"))
                        return
                    }

                    firstly {
                        return myFunc(info: info)
                    }
                    .then { _ -> () in
                        fulfill(())
                    }
                    .catch { error2 in
                        reject(error2)
                    }

                default:
                reject(error)
            }
        }
    }
}