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Loop may offer in-built SwiftUI integration on Apple platforms without creating an extra "LoopUI" package.

Loop only needs to provide standard data funnels to connect feedback loops with SwiftUI, and has no involvement in UI concerns except for the two characters in import SwiftUI. Everything else is SwiftUI's declarative UI realm (data to virtual DOM, vDOM to native view, etc). That is in contrast to our UIKit sibling ReactiveCocoa, which is a heavy UI-focused library that (1) attempted to solve AppKit/UIKit reactive programming at a micro level (KVO-like property bindings), and (2) wraps parts of Objective-C dynamism into friendly Swift APIs.

Since SwiftUI is shipped with the system, no friction is incurred for dependency management on users' end. All these collectively makes it perfect for Loop to offer straightly the said utilities.

Such integration should be excluded from Linux builds.

Concepts

Concepts are built upon the implicit behavior of DynamicProperty, which serves as a clue for SwiftUI runtime to look inside the property wrapper, so as to pick up embedded special wrappers like @State, @ObservedObject and @Environment.

This enables us to build custom property wrappers that provide simple dev experience, while hiding the heavy lifting of bridging feedback loops to SwiftUI world.

Direct state binding like @ObservedObject:

Bound view pseudo code

typealias WeatherStore = Store<WeatherState, WeatherAction>

struct WeatherView: View {
    @WeatherStore.Binding
    var state: WeatherState

    init(store: WeatherStore) {
      _state = store.binding()
    }

    var body: some Body {
        VStack {
            Spacer()

            Text("Current temperature: \(state.temperature)")
                + Text(" \(state.unit)").font(.system(size: 10.0)).baselineOffset(7.0)
            Spacer()
            Button()
                action: { self.$state.perform(.refresh) }
                label: { Text("Refresh 🔄") }

            Spacer()
    }
}

SwiftUI environment injected state bindings

Note: Unlike @State and @ObservedObject, it hasn't been tested whether @EnvironmentObject would work.

Bound view pseudo code

typealias WeatherStore = Store<WeatherState, WeatherAction>

struct WeatherView: View {
    @WeatherStore.EnvironmentBinding
    var state: WeatherStore.State

    var body: some Body {
        VStack {
            Spacer()

            Text("Current temperature: \(state.temperature)")
                + Text(" \(state.unit)").font(.system(size: 10.0)).baselineOffset(7.0)
            Spacer()
            Button()
                action: { self.$state.perform(.refresh) }
                label: { Text("Refresh 🔄") }

            Spacer()
    }
}

Parent view pseudo code

typealias WeatherStore = Store<WeatherState, WeatherAction>
let weatherStore = WeatherStore()

struct ContentView: View {
    var body: some Body {
        WeatherView()
            .environmentObject(weatherStore)
    }
}

Partial store

Already supported via Store.view(value:event:). e.g. injecting via @EnvironmentBinding a partial store that exposes only state & events related to radar images.

typealias WeatherStore = Store<WeatherState, WeatherAction>
let weatherStore = WeatherStore()

struct ContentView: View {
    var body: some Body {
        RadarView()
            .environmentObject(
                weatherStore.view
                    value: \WeatherState.radarImages
                    event: WeatherAction.radar
            )
    }
}

Resurrecting old proposal from @inamiy babylonhealth/ReactiveFeedback#41

This is an additive change to add Optional<Event> argument in Feedback so that unnecessary intermediate states will no longer be required.

Event-driven feedback will be useful for following scenarios, without needing to add a new state and then transit (and transit back again):

• Logging
• Analytics
• Routing
• Image loader (but not managing its internal states)

This is a change from Moore model to (kind of) Mealy model as discussed in babylonhealth/ReactiveFeedback#32 (review) .

Please note that reducer and feedback are still in sequence, not parallel.

Also, please note that Optional<Event> is used here as a workaround since it requires more breaking changes to minimize into non-optional Event.

At this point I do not see a value having two sightly different implementation of the same thing.

I proposing to remove old system operator that takes scheduler in favour of new queue-drain event processing.

FeedbackLoop.Feedback -> Feedback