RxErrorTracker

An RxSwifty approach to error handling.

RxErrorTracker provides a clean, integrated and easy to use approach to error handling. It is based on RxSwift and represents an observable sequence of errors Rx style. The main benefit is to enable a single point of entry for dealing with the multiple errors that applications need to handle.

Usage

You can push new errors to the RxErrorTracker sequence by directly emiting new errors or by tracking the errors of another observable sequence. If you’ve used RxSwift’s ActivityIndicator, RxErrorTracker will feel familiar.

You can define reset times after which the RxErrorTracker will signal nil.

Additionally, an RxErrorTracker can be initialized with a reset signal which will reset the tracker whenever this signal produces a new value. This is particularly useful if you want to bound an error to a specific context. Say, an error which makes sense in the context of a view but should be dismissed when view disappears. (If you’re using MVVM RxViewModel is a great complement to this feature)

let errorTracker = RxErrorTracker()
let disposeBag = DisposeBag()
let id: Int? = 1

guard let _id = id else {
    errorTracker.onNext(Error.Internal)
    return
}

fetchUserRequest(withId: _id)
    .trackError(errorTracker, resetTime: 5)
    .subscribe()
    .addDisposableTo(disposeBag)

Then you can observe the RxErrorTracker and handle the errors however you want.

let errorBannerMessageUpdate = errorTracker
    .map { error -> String in
        guard let _error = error as? Error else {
            return ""
        }
        return _error.description
    }

let errorBannerVisibilityUpdate = errorTracker
    .map { error -> Bool in
        return error != nil
    }

You can be as granular as you need in tracking the errors. For more complex scenarios you could have multiple RxErrorTracker’s and merge or combine them in order to set error priorities

let errorBannerStateUpdate = Driver.combineLatest(
    noConnectionErrorTracker,
    serverAPIErrorTracker,
    internalErrorTracker) {($0, $1, $2)}
    .map { (noConnectionError, serverError, internalError) -> ErrorBannerState in

        // The order of the if clauses will define priorities

        if noConnectionError != nil {return .NoConnectionErrorBannerState}
        else if serverError != nil {return .ServerErrorBannerState(error: serverError)}
        else if internalError != nil {return .InternalErrorBannerState}

    }
}

Example

To run the example project, clone the repo, and run pod install from the Example directory first.

Installation

RxErrorTracker is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod "RxErrorTracker"

Author

Bruno Morgado, [email protected]

License

RxErrorTracker is available under the MIT license. See the LICENSE file for more info.