fun coldStream(): Flow<Int> = flow {
    println("開始發(fā)射")
    emit(1)
    emit(2)
    emit(3)
}
// 使用
suspend fun main() {
    val cold = coldStream()
    println("第一次收集:")
    cold.collect { println(it) } // 會觸發(fā)完整的發(fā)射流程
    println("第二次收集:")
    cold.collect { println(it) } // 會再次觸發(fā)完整的發(fā)射流程
}

suspend fun hotStreamExample() {
    val channel = Channel<Int>() // 熱流
    launch {
        println("開始發(fā)射")
        channel.send(1)
        channel.send(2)
        channel.send(3)
        channel.close()
    }
    delay(100) // 確保發(fā)射已經(jīng)開始
    println("第一次收集:")
    channel.consumeEach { println(it) } // 只能收到剩余數(shù)據(jù)
    // 第二次收集會失敗，因為Channel已經(jīng)被關(guān)閉
}

fun fetchUserData(): Flow<User> = flow {
    // 只有收集時才會真正查詢數(shù)據(jù)庫
    val data = database.queryUsers()
    emitAll(data.asFlow())
}

// 使用StateFlow管理UI狀態(tài)
class ViewModel {
    private val _uiState = MutableStateFlow<UiState>(Loading)
    val uiState: StateFlow<UiState> = _uiState.asStateFlow()
    fun loadData() {
        viewModelScope.launch {
            _uiState.value = Loading
            try {
                val data = repository.fetchData()
                _uiState.value = Success(data)
            } catch (e: Exception) {
                _uiState.value = Error(e.message)
            }
        }
    }
}

val coldFlow = flow { /*...*/ }
// 轉(zhuǎn)為SharedFlow（熱流）
val sharedFlow = coldFlow.shareIn(
    scope = viewModelScope,
    started = SharingStarted.WhileSubscribed(),
    replay = 1
)
// 轉(zhuǎn)為StateFlow（熱流）
val stateFlow = coldFlow.stateIn(
    scope = viewModelScope,
    started = SharingStarted.WhileSubscribed(),
    initialValue = null
)

val hotChannel = Channel<Int>()
// 轉(zhuǎn)為Flow（冷流）
val coldFlow = hotChannel.consumeAsFlow()