RxSwift + optional

RxSwift+Optional.swift

// MIT License
//
// Copyright (c) 2016 Thane Gill <me@thanegill.com>
// Copyright (c) 2014-2017 Art.sy, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
// of the Software, and to permit persons to whom the Software is furnished to do
// so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

// https://github.com/RxSwiftCommunity/RxOptional/blob/447444e02ee6a657495753f57cdb2fdb329dea99/Source/Observable%2BOptional.swift
// Some code originally from here: https://github.com/artsy/eidolon/blob/24e36a69bbafb4ef6dbe4d98b575ceb4e1d8345f/Kiosk/Observable%2BOperators.swift#L42-L62
// Credit to Artsy and @ashfurrow

import RxSwift

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

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

extension Observable where Element: OptionalType {
    func filterNil() -> Observable<Element.Wrapped> {
        return flatMap { (element) -> Observable<Element.Wrapped> in
            if let value = element.value {
                return .just(value)
            } else {
                return .empty()
            }
        }
    }
}

Credit to Artsy and @ashfurrow

https://github.com/RxSwiftCommunity/RxOptional/blob/447444e02ee6a657495753f57cdb2fdb329dea99/Source/Observable%2BOptional.swift
https://github.com/artsy/eidolon/blob/24e36a69bbafb4ef6dbe4d98b575ceb4e1d8345f/Kiosk/Observable%2BOperators.swift#L42-L62