2.0.0 alpha 1

This is the first alpha release of ReactiveSwift 2.0. It requires Swift 3.1 (Xcode 8.3).

Changes

Modified Signal lifetime semantics (#355)

The Signal lifetime semantics is modified to improve interoperability with memory debugging tools. ReactiveSwift 2.0 adopted a new Signal internal which does not exploit deliberate retain cycles that consequentially confuse memory debugging tools.

A Signal is now automatically and silently disposed of, when:

1. the Signal is not retained and has no active observer; or
2. (New) both the Signal and its input observer are not retained.

It is expected that memory debugging tools would no longer report irrelevant negative leaks that were once caused by the ReactiveSwift internals.

SignalProducer resource management (#334)

SignalProducer now uses Lifetime for resource management. You may observe the Lifetime for the disposal of the produced Signal.

let producer = SignalProducer<Int, NoError> { observer, lifetime in
    if let disposable = numbers.observe(observer) {
        lifetime.observeEnded(disposable.dispose)
    }
}

Two Disposable-accepting methods Lifetime.Type.+= and Lifetime.add are provided to aid migration, and are subject to removal in a future release.

Signal and SignalProducer

1. All Signal and SignalProducer operators now belongs to the respective concrete types. (#304)

   Custom operators should extend the concrete types directly. SignalProtocol and SignalProducerProtocol should be used only for constraining associated types.

2. combineLatest and zip are optimised to have a constant overhead regardless of arity, mitigating the possibility of stack overflow. (#345)

3. flatMap(_:transform:) is renamed to flatMap(_:_:). (#339)

4. promoteErrors(_:)is renamed to promoteError(_:). (#408)

5. Event is renamed to Signal.Event. (#376)

6. Observer is renamed to Signal.Observer. (#376)

Action

1. Action(input:_:), Action(_:), Action(enabledIf:_:) and Action(state:enabledIf:_:) are renamed to Action(state:execute:), Action(execute:), Action(enabledIf:execute:) and Action(state:enabledIf:execute:) respectively. (#325)

Properties

1. The memory overhead of property composition has been considerably reduced. (#340)

Bindings

1. The BindingSource now requires only a producer representation of self. (#359)

2. The <~ operator overloads are now provided by BindingTargetProvider. (#359)

Disposables

1. SimpleDisposable and ActionDisposable has been folded into AnyDisposable. (#412)

2. CompositeDisposable.DisposableHandle is replaced by Disposable?. (#363)

3. The += operator overloads for CompositeDisposable are now hosted inside the concrete types. (#412)

Bag

1. Improved the performance of Bag. (#354)

2. RemovalToken is renamed to Bag.Token. (#354)

Schedulers

1. Scheduler gains a class bound. (#333)

Lifetime

1. Lifetime.ended now uses the inhabitable Never as its value type. (#392)

Atomic

1. Signal and Atomic now use os_unfair_lock when it is available. (#342)

Additions

1. FlattenStrategy.race is introduced. (#233, kudos to @inamiy)

   race flattens whichever inner signal that first sends an event, and ignores the rest.

2. FlattenStrategy.concurrent is introduced. (#298, kudos to @andersio)

   concurrent starts and flattens inner signals according to the specified concurrency limit. If an inner signal is received after the limit is reached, it would be queued and drained later as the in-flight inner signals terminate.

3. New operators: reduce(into:) and scan(into:). (#365, kudos to @ikesyo)

   These variants pass to the closure an inout reference to the accumulator, which helps the performance when a large value type is used, e.g. collection.

4. Property(initial:then:) gains overloads that accept a producer or signal of the wrapped value type when the value type is an Optional. (#396)

Deprecations and Removals

1. The requirement BindingSource.observe(_:during:) and the implementations have been removed.

2. All Swift 2 (ReactiveCocoa 4) obsolete symbols have been removed.

3. All deprecated methods and protocols in ReactiveSwift 1.1.x are no longer available.

Acknowledgement

Thank you to all of @ReactiveCocoa/reactiveswift and all our contributors, but especially to @andersio, @calebd, @eimantas, @ikesyo, @inamiy, @Marcocanc, @mdiep, @NachoSoto, @sharplet and @tjnet. ReactiveSwift is only possible due to the many hours of work that these individuals have volunteered. ❤️