Custom RxSwift operator that maps and unwraps an optional value.

ObservableType+IgnoreNilMap.swift

import RxSwift

extension ObservableType {

    /// A map that unwraps an optional value, only continuing if the result is not nil.
    func ignoreNilMap<R>(transform: @escaping (E) -> R?) -> Observable<R> {
        return Observable.create { observer in
            return self.subscribe { element in
                switch element {
                case .next(let value):
                    guard let result = transform(value) else {
                        break
                    }

                    observer.onNext(result)
                case .error(let error):
                    observer.onError(error)
                case .completed:
                    observer.onCompleted()
                }
            }
        }
    }
}