التأثيرات والتبعيات

لماذا توجد التأثيرات

import ComposableArchitecture

// Reducer stays pure; side effects are values it returns.
// Returning .none means no further work.

إعادة .none

import ComposableArchitecture

Reduce { state, action in
    switch action {
    case .incrementTapped:
        state.count += 1
        return .none
    }
}

‏Effect.run للعمل غير المتزامن

import ComposableArchitecture

Reduce { state, action in
    switch action {
    case .reloadTapped:
        return .run { send in
            let value = try await loadNumber()
            await send(.responseReceived(value))
        }
    case let .responseReceived(value):
        state.count = value
        return .none
    }
}

إعادة النتائج على هيئة إجراءات

import ComposableArchitecture

.run { send in
    let result = try await fetch()
    await send(.dataLoaded(result))
}
// .dataLoaded is then handled by the reducer to set state.

معالجة الأخطاء في التأثيرات

import ComposableArchitecture

.run { send in
    let value = try await loadNumber()
    await send(.responseReceived(value))
} catch: { error, send in
    await send(.loadFailed)
}

لماذا تهم التبعيات

import ComposableArchitecture

// Instead of calling APIClient.shared directly,
// inject it as a dependency so tests can replace it.

غلاف الخاصية @Dependency

import ComposableArchitecture

@Reducer
struct TimerFeature {
    @ObservableState
    struct State: Equatable { var seconds = 0 }
    enum Action { case start, tick }

    @Dependency(\.continuousClock) var clock

    var body: some ReducerOf<Self> {
        Reduce { state, action in .none }
    }
}

استخدام تبعية في تأثير

import ComposableArchitecture

var body: some ReducerOf<Self> {
    Reduce { state, action in
        switch action {
        case .start:
            return .run { send in
                for await _ in self.clock.timer(interval: .seconds(1)) {
                    await send(.tick)
                }
            }
        case .tick:
            state.seconds += 1
            return .none
        }
    }
}

تعريف تبعيتكم الخاصة

import ComposableArchitecture

struct NumberClient {
    var fetch: () async throws -> Int
}

extension NumberClient: DependencyKey {
    static let liveValue = NumberClient {
        try await loadNumber()
    }
}

extension DependencyValues {
    var numberClient: NumberClient {
        get { self[NumberClient.self] }
        set { self[NumberClient.self] = newValue }
    }
}

حقن التبعية المخصصة

import ComposableArchitecture

@Reducer
struct NumberFeature {
    @ObservableState
    struct State: Equatable { var value = 0 }
    enum Action { case reload, response(Int) }

    @Dependency(\.numberClient) var numberClient

    var body: some ReducerOf<Self> {
        Reduce { state, action in
            switch action {
            case .reload:
                return .run { send in
                    let n = try await numberClient.fetch()
                    await send(.response(n))
                }
            case let .response(n):
                state.value = n
                return .none
            }
        }
    }
}

إلغاء التأثيرات

import ComposableArchitecture

enum CancelID { case timer }

// Start a cancellable effect:
.run { send in /* ... */ }
    .cancellable(id: CancelID.timer)

// Stop it from another action:
.cancel(id: CancelID.timer)

مراجعة سريعة: التأثيرات والنتائج

مراجعة: التأثيرات والاعتماديات

import ComposableArchitecture

// Recap: pure reducer + Effect.run for async work
// + @Dependency for testable, injectable services.