RxJava：链接两个平面图

Question

我有一个方法 getListFromDatabase() returns Single<List<User>> users，我想做的是：

getListFromDatabase()
.flatMap(// send list to another server)
.flatMap(// check if there are users that I have to added manually from a bundle, here I needs database connexion so I have to do this asynchronously, and I need the list I just retrieved)
.observeOn(AndroidSchedulers.mainThread())
.subscribe(// handle onSuccess, onError etc.)

但是在第一个flatMap中，它一直告诉我missing return statement。我不知道什么是正确的语法？

Answer 1

getListFromDatabase()
.flatMap(users -> sendAnotherService().map(ingoreResult -> users))
.flatMap(// check if there are users that I have to added manually from a bundle, here I needs database connexion so I have to do this asynchronously, and I need the list I just retrieved)
.observeOn(AndroidSchedulers.mainThread())
.subscribe(// handle onSuccess, onError etc.)

where sendAnotherService() return 带有任何类型参数的单个。