从 firebase 火库返回 Observable

Question

嘿伙计们，我是响应式风格的新手，无法将 firebase 查询快照转换为可观察的，您将如何完成此 function？ ：

    override fun GetAllRiders() : Observable<ArrayList<Rider>> {

    var riders = database.collection(DATABASE_COLLECTION_RIDERS)
    riders.addSnapshotListener { querySnapshot, firebaseFirestoreException ->
        val riderList = querySnapshot?.toList()
    }

    return ...
}

Answer 1

您必须创建 Observable 并使用回调（如onNext或onError ）来通知新数据出现

override fun getAllRiders() = Observable.create { emitter ->
    var riders = database.collection(DATABASE_COLLECTION_RIDERS)

    // here you attach a callback which will be called when .dispose() is called
    // or setDisposable (but only one of them at a time! otherwise you're observable will get disposed while creating)
    emitter.setCancelable { riders.cancel() /* don't remember the specifics :( */ }

    riders.addSnapshotListener { querySnapshot, firebaseFirestoreException ->
        if (!emitter.isCancelled) {
            if (firebaseFirestoreException != null) {
                // callback for exceptions. here you can pass your Throwable
                emitter.onError(firebaseFirestoreException)
            } else {
                val riderList = querySnapshot?.toList()

                // Callback which will populate passed data to your .subscribe callback
                emitter.onNext(riderList)
            }
        }
    }
}

PS 我鼓励你坚持使用kotlin 代码风格。 函数应该以小写首字母命名；）