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Getting "use of undeclared type 'NoError'" with ReactiveCocoa

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 I keep hitting minor bumps as API and tutorials seems to be outdated quickly.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.

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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.

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Filuren Avatar asked Feb 04 '16 15:02

Filuren


3 Answers

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: ())
}
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CodeBender Avatar answered Oct 23 '22 08:10

CodeBender


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.NoError in 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
like image 30
dfrib Avatar answered Oct 23 '22 06:10

dfrib


If you add "import Results" to the top of the page above your class, NoError will no longer be an undeclared type!

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KeithRussell Avatar answered Oct 23 '22 07:10

KeithRussell