在协程流程中组合多个 Firestore 任务

Question

下面的代码通过使用协程流从 firestore 获取数据，给出了我想要的结果。

 suspend fun getFeedPer() = flow<State<Any>> {
    emit(State.loading())

    val snapshot = dbRef.collection("FeedInfo/FeedPercent/DOC/")
        .whereGreaterThanOrEqualTo("bodyWeight", 0.80)
        .limit(1)
        .get().await()
    val post = snapshot.toObjects(FeedPer::class.java)
    Log.d("TAG", "getFeedPer: ${snapshot.documents[0].id}")
    Log.d("TAG", "getFeedPer: $post")
    emit(State.success(post))
}.catch {
    emit(State.failed(it.message.toString()))
}.flowOn(Dispatchers.IO)

现在我正在尝试向我的查询添加一个过滤器。为此，我正在使用任务。

    val docRef=dbRef.collection("FeedInfo/FeedPercent/DOC/")
    val task1=docRef.whereGreaterThanOrEqualTo("bodyWeight", 0.80)
        .limit(1).get()
    val task2=docRef.whereLessThanOrEqualTo("bodyWeight", 0.80)
        .limit(1).get()

现在如何通过协程流程来完成它。

请帮忙谢谢

Answer 1

您必须将任务放入 coroutineScope 中，其他一切都将与以前相同。

 emit(State.loading())

    var eMsg = ""
    val docRef = dbRef.collection("FeedInfo/FeedPercent/DOC/")
    val task1 = docRef.whereGreaterThanOrEqualTo("bodyWeight", 0.80)
        .limit(1).get()
    val task2 = docRef.whereLessThanOrEqualTo("bodyWeight", 0.80)
        .orderBy("bodyWeight", Query.Direction.DESCENDING)
        .limit(1).get()
   /** Need to do query Direction here to get correct data*/

    coroutineScope {
        val allTask: Task<List<QuerySnapshot>> = Tasks.whenAllSuccess(task1, task2)

        allTask.addOnSuccessListener {

            for (querySnapshot in it) {
                for (documentSnapshot in querySnapshot) {
                    /** Do your code to get the data */
                }
            }
            
        }.await()
        
        allTask.addOnFailureListener {
            eMsg = it.message.toString()                
        }
        /** Emitting flow based on task status **/

        if (allTask.isSuccessful) {
            emit(State.success(WhatEverItIs))
        } else {
            emit(State.failed(eMsg))
        }

    }
}.catch {
    emit(State.failed(it.message.toString()))
}.flowOn(Dispatchers.IO)