Coverage Summary for Class: CombinedStateFlow (dev.shreyaspatil.permissionFlow.utils.stateFlow)

1 /**
2  * Copyright 2022 Shreyas Patil
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package dev.shreyaspatil.permissionFlow.utils.stateFlow
17 
18 import kotlinx.coroutines.coroutineScope
19 import kotlinx.coroutines.flow.Flow
20 import kotlinx.coroutines.flow.FlowCollector
21 import kotlinx.coroutines.flow.StateFlow
22 import kotlinx.coroutines.flow.combine
23 import kotlinx.coroutines.flow.stateIn
24 
25 /**
26  * [StateFlow] which delegates [flow] to use it as StateFlow and uses [getValue] to calculate value
27  * at the instant.
28  */
29 private class CombinedStateFlow<T>(
30     private val getValue: () -> T,
31     private val flow: Flow<T>,
32 ) : StateFlow<T> {
33     override val replayCache: List<T>
34         get() = listOf(value)
35 
36     override val value: T
37         get() = getValue()
38 
39     override suspend fun collect(collector: FlowCollector<T>): Nothing = coroutineScope {
40         flow.stateIn(this).collect(collector)
41     }
42 }
43 
44 /** Returns implementation of [CombinedStateFlow] */
45 internal fun <T> combineStates(
46     getValue: () -> T,
47     flow: Flow<T>,
48 ): StateFlow<T> = CombinedStateFlow(getValue, flow)
49 
50 /** Combines multiple [StateFlow]s and transforms them into another [StateFlow] */
51 internal inline fun <reified T, R> combineStates(
52     vararg stateFlows: StateFlow<T>,
53     crossinline transform: (Array<T>) -> R,
54 ): StateFlow<R> =
55     combineStates(
56         getValue = { transform(stateFlows.map { it.value }.toTypedArray()) },
57         flow = combine(*stateFlows) { transform(it) },
58     )