Source observable sequence has completed and no further element will be bound. This may be something unexpected.

[adamsmaka]

Just updated RxSwift from 3.4 to 4.0 beta.1 and started to seeing this warning in the console:

Source observable sequence has completed and no further element will be bound. This may be something unexpected.

What does it means? It wasn't a case before and I have no idea what causing it. :)

[kzaher]

public struct Binder<Value>: ObserverType {
    public typealias E = Value
    
    private let _binding: (Event<Value>) -> ()

    /// Initializes `Binder`
    ///
    /// - parameter target: Target object.
    /// - parameter scheduler: Scheduler used to bind the events.
    /// - parameter binding: Binding logic.
    public init<Target: AnyObject>(_ target: Target, scheduler: ImmediateSchedulerType = MainScheduler(), binding: @escaping (Target, Value) -> ()) {
        weak var weakTarget = target

        _binding = { event in
            switch event {
            case .next(let element):
                _ = scheduler.schedule(element) { element in
                    if let target = weakTarget {
                        binding(target, element)
                    }
                    return Disposables.create()
                }
            case .error(let error):
                bindingError(error)
            case .completed:
                #if DEBUG
                    print("Source observable sequence has completed and no further element will be bound. This may be something unexpected.")
                #endif
                break
            }
        }
    }

    /// Binds next element to owner view as described in `binding`.
    public func on(_ event: Event<Value>) {
        _binding(event)
    }

    /// Erases type of observer.
    ///
    /// - returns: type erased observer.
    public func asObserver() -> AnyObserver<Value> {
        return AnyObserver(eventHandler: on)
    }
}

[adamsmaka]

This may be something unexpected.

In my case it's expected and I got a lot of warnings in my console now.

[RamwiseMatt]

I'm doing the same thing (binding to an Observable that completes), and this warning doesn't really contribute much. Is the reason behind this warning that binding should only happen on hot observables?

[kzaher]

I think that binding something finite is weird IMHO and is probably a bug.

However, I can remove this warning for the next release.

[kzaher]

Removed.