Grouping TCA Presented Stores into Single

3 min readMay 24, 2024

Today I followed the tutorial and found new one, so I improved my Store with the introduced way.

Search Store had used Add Store directly.

@Reducer
public struct SearchCharacterStore {
    @ObservableState
    public struct State: Equatable {
        @Presents
        public var addDateState: AddDateStore.State?

    public enum Action {
        case addDateAction(PresentationAction<AddDateStore.Action>)

We need to write bolierplate codes to add another nested stores and we can’t ensure only one child store is created now. But TCA provides us a convenient way, it is @Reducer

First define nested Destination enum with the macro, don’t forget .equatable

public extension SearchCharacterStore {
    @Reducer(state: .equatable)
    public enum Destination {
        case addCharacter(AddDateStore)
    }
}

And add destination definitions into the Store

@ObservableState
    public struct State: Equatable {
        ...
        @Presents
        var destination: Destination.State?
        ...

    public enum Action {
        case destination(PresentationAction<Destination.Action>)

Compiler will emit error if we don’t give .equatable. Reducer macro will create State and Action automatically for us 😀. So now we can replace PresentationAction Definitions.

// @Presents public var addDateState: AddDateStore.State?
...
// case addDateAction(PresentationAction<AddDateStore.Action>)

This task will raise compile errors.

Therefore we have to modify Reduce also. Replace lines of the code modifying state of specific store to the code using destination state.

state.destination = .addCharacter(.init(selectedDate: now))

The destination will provide autocompletion!

It generates also presented actions.

case let .destination(.presented(.addCharacter(.delegate(.saveDate(savedDate: selectedDate))))):
//  case .addDateAction(.presented(.delegate(.saveDate(let selectedDate)))):
    return .run { @MainActor send in
        database.insert(Item(timestamp: selectedDate))
    }
case .destination:
//  case .addDateAction:
    return .none

Final task is to replace IfLet . I created a new Store in the closure like this.

.ifLet(\.$addDateState, action: \.addDateAction) {
    AddDateStore()
}

It is necessary no more. Just fill with only destination.

.ifLet(\.$destination, action: \.destination)

Testing

I wrote tests in previous article, so I modified also it.

I can modify this test code

await store.send(.addButtonTapped) { [now = now] in
    $0.destination = .init(selectedDate: now)
}

like this

await store.send(.addButtonTapped) { [now = now] in
    $0.destination = .addCharacter(.init(selectedDate: now))
}

And this

await store.send(\.addDateAction.saveButtonTapped) {
    $0.addDateState?.isSaving = true
}

can be replaced with

await store.send(\.destination.addCharacter.saveButtonTapped) {
    $0.destination?.addCharacter?.isSaving = true
}

There is no special thing, just replace all accessor to the state or the action with destination and press .

That’s all!

Ah… I found one special case. I handled dismiss dependency like following

await store.receive(\.destination.presented.addCharacter.dismiss)

However it is not working.

Because I don’t have to know from where dismiss came? Also the state checking should use destination, not destination?.addCharacter.

await store.receive(\.destination.dismiss) {
    $0.destination = nil
}

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Troubleshootings

does not conform to protocol ‘Equatable’

@Reducer(state: .equatable)

state autocompletion is not working

Remove or comment out presented cases

Enum case in a public enum uses an internal type

Make Destination public

public enum Destination