TCA migration questions and some experiences from 0.54 to 1.0

[marcuswu0814]

If someone like me wanna find some guide to migrate to 1.0 version, it’s some of my experiences when I adapt to my projects.

Also had some questions in sections if someone can share your advices, really thanks for that!

1. Replace ReducerProtocol with Reducer

2. Replace EffectTask with Effect

3. Using closure base api for init a Store

From:

ContentView(
    store: Store(
        initialState: AppFeature.State(),
        reducer: AppFeature() // <- ‼️ Remove this 
    )
)

To:

ContentView(
    store: Store(
        initialState: AppFeature.State()
    ) { // <- Trailing closure with Reducer here 
        AppFeature()
    }
)

important
Question: But why? Any benefit for this change?

4. Sending action to Store immediately

In past time we need to send action to a ViewStore although you didn’t need observe any changes.

In 1.0, you just need to send the action to Store.

From:

Button("Some Button") {
    ViewStore(store).send(.delegate(.tap))
}

To:

Button("Some Button") {
    store.send(.delegate(.tap))
}

5. @BindableState to @BindingState

Replace all @BindableState to @BindingState in your State struct.

In your view, your need to change binding syntax

From:

TextEditor(text: store.binding(\.$text))

To:

TextEditor(text: store.$text)

important
Question: In past, I used ViewStore(store).binding(\.$text) in some where I didn’t have completely ViewStore causing by WithViewStore(...).

I know there is a guide for this situation but for me it’s too many boilerplate ViewState code need to write and hope can be solve by Swift Macro soon.

Is this the only way I can do? Or can I still using ViewStore(store, observe: { $0 }).$text in my view?

6. Loose coupling of Combine

Lots of feature be replace with Swift Concurrency with async/await, if your API is still using Publisher, you can follow the tip and it still work, if you need the eraseToEffect() or catchToEffect(), just adding the extension back for your situation.

In my case, my API using RxSwift’s Single trait and I using the follow extension work with Effect:

public extension Single where Trait == SingleTrait {
    func catchToEffect<T>(
      _ transform: @escaping (Result<Element, Error>) -> T
    ) -> Effect<T> {
        .publisher {
            publisher.map(
                withEscapedDependencies { escaped in
                    { action in
                        escaped.yield {
                            transform(.success(action))
                        }
                    }
                }
            )
            .catch { Just(transform(.failure($0))) }
        }
    }
}

The publisher property of Single if from RxCombine.

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I’m not sure is all of my change is best practice or correctly, if there had any problems, please feel free to let me know, and also glad to your sharing!

[mbrandonw]

Hi @marcuswu0814, thank you for writing this up to share with everyone.

I will say, though, that we highly recommended people upgrade to 0.58.0 before going to 1.0. That would have helped catch most of these things as simpler deprecation warnings rather than hard, incomprehensible errors.