A combine operator for transforming unwrapped values and passing along nil values

Publisher+Unwrap.swift

protocol OptionalType {
    associatedtype Wrapped
    var value: Wrapped? { get }
}

extension Optional: OptionalType {
    public var value: Wrapped? {
        return self
    }
}

extension Publisher where Output: OptionalType {
    
    func mapUnwrapped<Result>(_ transform: @escaping (Output.Wrapped) -> Result?) -> Publishers.Map<Self, Result?> {
        map { $0.value.flatMap(transform) }
    }
    
}