RACsignal.toSignalProducer() unavailable

[opfeffer]

The README.md reads:

“Hot” RACSignals cannot be directly converted into Signals, because any RACSignal subscription could potentially involve side effects. To obtain a Signal, use RACSignal.toSignalProducer followed by SignalProducer.start, which will make those potential side effects explicit.

I have an instance of RACSignal due to a mixed-language project. Looking through XCode's auto-completion suggestions, I'm not seeing anything like toSignalProducer.

Could I get a code example of how to turn a RACSignal back to Signal?

Thanks!

[andersio]

You can produce a Signal from a SignalProducer using startWithSignal. Note that the subscription side effect would run after the setUp closure is invoked, but before startWithSignal returns.

signal.toSignalProducer().startWithSignal { signal, interrupter in
    // Do your stuff with `signal`.
}

[opfeffer]

Thanks for getting back to me.

I'm afraid I didn't do a very good job describing my problem - I have an ObjC interface that looks like so:

 @property (nonatomic, strong, readonly) RACSignal<NSDictionary *> *events;

Now, my view/business layer is written in swift mostly and I'm trying to combine events with some other Swift-defined Signals. I was able to achieve the reverse, Swift->ObjC with ReactiveObjCBridge's extensions to SignalProtocol

 public func toRACSignal() -> RACSignal<Self.Value.Wrapped>

but I'm not sure how I can transform a RACSignal to a Signal?

In your response, you said signal.toSignalProducer().startWithSignal { ... }, but events.toSignalProducer() throws compiler warning:

What am I missing? Thanks!

[andersio]

https://github.com/ReactiveCocoa/ReactiveObjCBridge/blob/master/ReactiveObjCBridge/ObjectiveCBridging.swift#L122

It seems it was replaced by bridgedSignalProducer(from:) due to limitations of ObjC generics in Swift.

[NikKovIos]

@andersio @opfeffer
Could you please explain how to properly convert RACSignal to SignalProducer?
I've write something like

extension RACSignal {
    func toSignalProducer() -> SignalProducer<ValueType, AnyError> {
        return SignalProducer(self)
    }
}

but the compiler warn at it(

[andersio]

@NikKovIos

It should be ValueType? since ValueType is annotated as nullable for API backwards compatibility.

But AFAIK it still won’t compile — there are plenty of restrictions in Swift regarding Objective-C lightweight generics, and they are part of the rationale behind the current interop API besides Swiftification. At least last when we tried, the compiler rejects any extension referring to any generic parameter.

[NikKovIos]

Yes, so i manually wrap every rac_.. to SignalProducer (