问题
I am trying to learn ReactiveCocoa and have a hard time getting started. I keep hitting minor bumps as API and tutorials seems to be outdated quickly. Maybe I have the wrong impression.
Just trying to follow this I do not seem to have NoError.
It should be imported correctly, since I have access to Signal, rac_textSignal etc. but I don't know why NoError is not available.
Their documentation mentions NoError as well but that leads to a 404.
This transition to RAC4 mentions NoError as well. Why is NoError undeclared? I am using ReactiveCocoa 4.0.1.
Edit: I just added public enum NoError : ErrorType {} to the top of the file and it works now. I am not sure if this is a proper solution to the problem though. It is not mentioned in guides and tutorials that I should extend ErrorType myself.
回答1:
The reactive cocoa native NoError was removed in 4.0.1 in favour of antitypicals implementation in Result (adds NoError to Result, see this). See e.g. issue #2704
- https://github.com/ReactiveCocoa/ReactiveCocoa/issues/2704
We can see this explicitly used in the source files, e.g.
import enum Result.NoErrorin Property.swift.
Hence, you probably need to include (antitypicals) Result whenever you intend to use NoError. One suggested fix in the issue thread is
public typealias NoError = Result.NoError
回答2:
If you add "import Results" to the top of the page above your class, NoError will no longer be an undeclared type!
回答3:
If you are seeing this now with ReactiveSwift 6.0, they removed the dependency on Result, which removes NoError.
Per their release notes here, the solution is to now use Never.
- If you have used Result only as dependency of ReactiveSwift, remove all instances of import Result, import enum Result.NoError or import struct Result.AnyError and remove the Result Framework from your project.
- Replace all cases where NoError was used in a Signal or SignalProducer with Never
The following example code shows how this should look now:
import ReactiveSwift
func example() -> SignalProducer<Void, Never> {
return SignalProducer(value: ())
}
来源：https://stackoverflow.com/questions/35205550/getting-use-of-undeclared-type-noerror-with-reactivecocoa