Empty,Never,Throw运算

Throw运算

Never运算

Empty运算

extension Observable {
    public static func empty()->Observable {
        return Empty()
    }

    public static func never()->Observable {
        return Never()
    }
}

class Empty: Producer {
    override func subscribe(observer: O)->Disposable {
        observer.on(.Completed)
        return NoDisposable.instance
    }
}

class Never: Producer {
    override func subscribe(observer: O)->Disposable {
        return NoDisposable.instance
    }
}