Ignoring/filtering nil

Question

Is there an operator that can filter nil? The closest I've come is the solution mentioned here: https://github.com/ReactiveX/RxSwift/issues/209#issuecomment-150842686

Relevant excerpt:

public protocol OptionalType {
    func hasValue() -> Bool
}

extension Optional: OptionalType {
    public func hasValue() -> Bool {
        return (self != nil)
    }
}

public extension ObservableType where E: OptionalType {
    @warn_unused_result(message="http://git.io/rxs.uo")
    public func notNil() -> Observable<E> {
        return self.filter { $0.hasValue() }
    }
}

However, after .notNil(), E is still optional, so subsequent chained operators still see self as Observer<E> where E is optional. So I'm still needing an extra operator that does:

.map { (username: String?) -> String in
    return username!
}

I must be missing something. This seems like it would be a very common need.

Answer 1

In RxSwift 5 it's possible using compactMap from core library:

observable.compactMap { $0 }