ViewStore version without Combine/SwiftUI about reactiveswift-composable-architecture

[AndreiVidrasco]

Hi, yes, will check it later today or tomorrow.

Stay tuned

[maximkrouk]

Hi, I'm using this library with an iOS 11.4+ project. I think, that the problem should not be in the implementation. Can you provide more information about the errors you got?

[AndreiVidrasco]

Well, let's take as an example: https://github.com/trading-point/reactiveswift-composable-architecture/blob/master/Examples/TicTacToe/Sources/Views-UIKit/GameViewController.swift.

It uses inside viewDidLoad method

self.viewStore.produced.title
      .assign(to: \.text, on: titleLabel)

Definition of ViewStore is to conform to ObservableObject, which is part of Combine.

Are you using ViewStore to access properties inside the ViewController, or you use Store directly?

[mluisbrown]

Hi @AndreiVidrasco,
At my work we using this library, including ViewStore in a project that supports iOS 12 with no problem at all. In fact that was the whole purpose of the port, to be able to use it with iOS 12!

Even though ViewStore conforms to ObservableObject since the ObservableObject protocol is annotated with @available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *) this turns into a no-op and for iOS 12 builds there is no protocol conformance. We are not linking Combine in our app at all.

In our View Controllers we have things like:

        viewStore.produced.isContinueButtonEnabled
            .startWithValues { [weak self] in
                self?.continueButton.isEnabled = $0
            }

and:

        backButton.reactive
            .controlEvents(.primaryActionTriggered)
            .observeValues { [weak self] _ in
                self?.viewStore.send(.prevPage)
            }

Are you getting a particular compiler or build error when using ViewStore?

[mluisbrown]

We are not linking Combine in our app at all.

Regarding this, please see this comment in the README.

You will need to weak link Combine and SwiftUI, but they will never be loaded. I have tested this running on an iOS 12 simulator.

[mluisbrown]

The reason that the ObservableObject conformance was kept was so that this library could still be used with SwiftUI if you wanted to, on a version of the OS that supports it.

[maximkrouk]

Also SwiftUI embeds Combine, so it is enough to embed SwiftUI only.

And I did it in an XCodeUI-way by adding SwiftUI to target's frameworks with embed value: "Do Not Embed".
Then in build phases in "Link Binary With Libraries" phase I changed SwiftUI status from required to optional.

[AndreiVidrasco]

Ok, thank you very much for your help.

My setup is a bit more extreme (and experimental).
We're using this tool https://github.com/readdle/swift-android-toolchain Swift Android Toolchain to have business logic in Swift (in future with composable architecture)
Turns out that Reactive Swift is running already on Linux, which made running it on Android trivial. PointFree's case paths don't have any dependencies and they run out of box on Android.
So, last missing piece was this repo to add. And as you can imagine even weak-linking is not really an option.
But no worries, I thought that the stuff from Combine is actually mandatory needed.

I will just fork and remove all mentions from Combine and use it like

viewStore.produced.isContinueButtonEnabled
            .startWithValues { [weak self] in
                self?.continueButton.isEnabled = $0
            }

Thanks for your help, closing the issue

[mluisbrown]

Interesting use case. I hadn't considered using the lib on non-Apple platforms.

It might be possible to use conditional compilation do optionally exclude the Combine dependency completely.

I'll see what I can do 👍

[mluisbrown]

It might be as straightforward as using #if canImport(Combine). I will try this in a branch and let you know.

[AndreiVidrasco]

I tried initially to do that, with #if canImport, but stumbled on this issue with ViewStore's conformance.

I guess some could write

#if canImport(Combine) // or os(Android)
public final class ViewStore<State, Action> {
#else 
public final class ViewStore<State, Action>: ObservableObject {
#endif

But I thought that is too narrow use-case to submit a PR

[mluisbrown]

I just created the branch michael/if-can-import-combine which conditionally excludes Combine and SwiftUI stuff from ViewStore. Let me know if it works for you:

https://github.com/trading-point/reactiveswift-composable-architecture/tree/michael/if-can-import-combine

UPDATE:
It might be necessary to add canImport to all the source files in the SwiftUI source folder of ComposableArchitecture.

[AndreiVidrasco]

@mluisbrown
it's not that simple. #26
Yes, I added #if canImport(SwiftUI) everywhere, because it was indeed needed.

But there is also, os.signpost, which unfortunately doesn't work, but I don't know the solution for it, and since I don't really need it for my use case, I completely deleted the file.

Other changes that I made:

#if os(Linux) || os(Android)
    import let CDispatch.NSEC_PER_USEC
    import let CDispatch.NSEC_PER_SEC
#endif

inside Sources/ComposableArchitecture/Internal/Debug.swift

This part I deleted completely(again, don't really need for my use case):

extension UnsafeMutablePointer where Pointee == os_unfair_lock_s {
  @inlinable @discardableResult
  func sync<R>(_ work: () -> R) -> R {
    os_unfair_lock_lock(self)
    defer { os_unfair_lock_unlock(self) }
    return work()
  }
}

And I think that's all changes. Now, the swift-android-toolchain is a bit behind, it works only on Swift 5.0.3, so I needed to add explicit return in a few places, but I don't think it's needed to add in the library, because there is a plan to update swift-android-toolchain.

[mluisbrown]

Ok, I merged your PR into my branch 👍

But there is also, os.signpost, which unfortunately doesn't work, but I don't know the solution for it, and since I don't really need it for my use case, I completely deleted the file.

I added #if canImport(os) around the ReducerInstrumentation.swift file, which should solve this.

For the use of os_unfair_lock I guarded the code with #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS).

So, apart from the explicit returns this should be enough. Are you able to check it in your environment?

[AndreiVidrasco]

Hi,

Sorry for taking this long. Yes, looks like it's working. The moment swift-android-toolchain will be updated to Swift 5.3 it's gonna be possible to use this out of box.

[mluisbrown]

Nice! I'm going to turn the branch into a PR then, and try to get CI running on Linux for it. Thanks for your help!