在移动端开发实现Redux以Bank为例

// State.kt
data class BankingState(
    val balance: Double = 0.0, // 账户余额，默认为 0.0
    val recentTransactions: List<String> = emptyList() // 最近交易列表，默认为空
    // ... 其他状态字段
)

// Action.kt
sealed class BankingAction {
    //存款动作，带存款金额
    data class Deposit(val amount: Double) : BankingAction()
    //取款动作，带取款金额
    data class Withdrawal(val amount: Double) : BankingAction()
    //加载交易记录，带交易记录列表
    data class SetTransactions(val transactions: List<String>) : BankingAction()
    //其他Action
}

// Reducer.kt
val bankingReducer: Reducer<BankingState> = { state, action ->
    //Reducer根据Action的类型和数据计算新的状态
    when (action) {
        is BankingAction.Deposit -> {
            //处理存款：创建一个新的状态，金额加到余额
            state.copy(balance = state.balance + action.amount)
        }
        is BankingAction.Withdrawal -> {
             //处理取款：创建一个新的状态，从余额中减去金额
             //注意：实际银行需要更复杂的逻辑处理支出、手续费等
            state.copy(balance = state.balance - action.amount)
        }
        is BankingAction.SetTransactions -> {
             //处理设置交易记录Action：创建一个新的状态，更新交易列表
            state.copy(recentTransactions = action.transactions)
        }
        else -> {
            //返回当前状态（不改变）
            state
        }
    }
}

// AppStore.kt
val appStore = createStore(bankingReducer, BankingState())

//BankingScreen.kt
@Composable
fun BankingScreen() {
    //selectState只监听Store中关心的那个部分状态
    //balanceState是State<Double>，当Store中余额变化时更新
    val balanceState = selectState(appStore) { state -> state.balance }
    val currentBalance = balanceState.value //获取当前余额
    //transactionsState是State<List<String>>，当Store中交易记录变化时更新
    val transactionsState = selectState(appStore) { state -> state.recentTransactions }
    val recentTransactions = transactionsState.value //获取交易记录列表
    //rememberDispatcher获取Store的dispatch函数
    val dispatch = rememberDispatcher(appStore)
    // 模拟加载交易记录（处理VM或Effect处理）
    LaunchedEffect(Unit) {
        //首次出现时，模拟加载交易记录并分发Action
        //网络请求的结果
        val loadedTransactions = listOf("Deposit +100.0", "Withdrawal -50.0", "Deposit +200.0")
        dispatch(BankingAction.SetTransactions(loadedTransactions))
    }
    Column(
        modifier = Modifier
            .fillMaxSize()
            .padding(16.dp),
        horizontalAlignment = Alignment.CenterHorizontally
    ) {
        Text(text = "当前余额:", fontSize = 18.sp)
        Text(
            text = "$${String.format("%.2f", currentBalance)}", //格式化余额显示
            fontSize = 24.sp,
            fontWeight = FontWeight.Bold,
            modifier = Modifier.padding(bottom = 16.dp)
        )
        Row(
            horizontalArrangement = Arrangement.spacedBy(16.dp)
        ) {
            Button(onClick = {
                //点击存款按钮，分发Deposit Action (假设存入100)
                dispatch(BankingAction.Deposit(100.0))
            }) {
                Text("存款 +100")
            }
            Button(onClick = {
                //点击取款按钮，分发Withdrawal Action (假设取出50)
                dispatch(BankingAction.Withdrawal(50.0))
            }) {
                Text("取款 -50")
            }
        }
        Spacer(modifier = Modifier.height(24.dp))
        Text(text = "最近交易:", fontSize = 18.sp, modifier = Modifier.align(Alignment.Start))
        LazyColumn(
            modifier = Modifier.fillMaxWidth()
        ) {
            items(recentTransactions) { transaction ->
                Text(text = transaction, modifier = Modifier.padding(vertical = 4.dp))
            }
        }
    }
}