如何使用RxJava将多个对象转换为一个对象？
如何使用RxJava将多个对象转换为一个对象？
提问于 2018-10-25 05:06:56
我有一个日历对象，里面有多个不同对象的列表，比如：，Estimate，WorkOrder和BlockTime。
因此，为了显示所有这些Calendar事件，我计划创建类型为event的CalendarItem对象并添加该事件。
public class CalendarItem {
private int type;
private Task task;
private Estimate estimate;
private WorkOrder workOrder;
private BlockTime blockTime;
public CalendarItem() {
}
}我有这个RxJava函数：
Disposable disposable = calendarRepository.getCalendar(startDate, endDate)
.subscribeOn(Schedulers.io())
.flatMap((Function<Calendar, Publisher<List<CalendarItem>>>) calendar -> {
List<Task> tasks = calendar.getTasks();
List<WorkOrder> workOrders = calendar.getWorkOrders();
List<BlockTime> blockTimes = calendar.getBlockTimes();
List<Estimate> estimates = calendar.getEstimates();
List<CalendarItem> calendarItems = new ArrayList<>();
if(tasks != null) {
for(Task t : tasks) {
CalendarItem item = new CalendarItem();
item.setType(Constants.CALENDAR_TASK);
item.setTask(t);
calendarItems.add(item);
}
}
if(workOrders != null) {
for(WorkOrder w : workOrders) {
CalendarItem item = new CalendarItem();
item.setType(Constants.CALENDAR_WORK_ORDER);
item.setWorkOrder(w);
calendarItems.add(item);
}
}
if(estimates != null) {
for(Estimate e : estimates) {
CalendarItem item = new CalendarItem();
item.setType(Constants.CALENDAR_ESTIMATE);
item.setEstimate(e);
calendarItems.add(item);
}
}
if(blockTimes != null) {
for(BlockTime b : blockTimes) {
CalendarItem item = new CalendarItem();
item.setType(Constants.CALENDAR_BLOCKED_TIME);
item.setBlockTime(b);
calendarItems.add(item);
}
}
return Flowable.just(calendarItems);
})
.observeOn(AndroidSchedulers.mainThread())
.subscribe(calendarItems -> view.displayCalendar(calendarItems), view::handleError);如何改进flatMap()运算符中的代码？
回答 2
Stack Overflow用户
发布于 2018-10-25 10:10:18
如果先更改CalendarItem以静态方式创建它呢？
public class CalendarItem {
private int type;
private Task task;
private Estimate estimate;
private WorkOrder workOrder;
private BlockTime blockTime;
// Change it to private.
// In the future, we will only create this object through static methods.
private CalendarItem() {
}
public static CalendarItem fromTask(Task t) {
CalendarItem item = new CalendarItem();
item.setType(Constants.CALENDAR_TASK);
item.setTask(t);
return item;
}
public static CalendarItem fromWorkOrder(WorkOrder w) {
CalendarItem item = new CalendarItem();
item.setType(Constants.CALENDAR_WORK_ORDER);
item.setWorkOrder(w);
return item;
}
public static CalendarItem fromEstimate(Estimate e) {
CalendarItem item = new CalendarItem();
item.setType(Constants.CALENDAR_ESTIMATE);
item.setEstimate(e);
return item;
}
public static CalendarItem fromBlockTime(BlockTime b) {
CalendarItem item = new CalendarItem();
item.setType(Constants.CALENDAR_BLOCKED_TIME);
item.setBlockTime(b);
return item;
}
...
}如果您可以使用Java Optional或Stream，则可以编写更简洁的代码。(安卓上也有像Lightweight-Stream-API这样的库。)
Disposable disposable = calendarRepository.getCalendar(startDate, endDate)
.subscribeOn(Schedulers.io())
.map(calendar -> {
List<CalendarItem> calendarItems = new ArrayList<>();
// tasks
calendarItems.addAll(Optional.ofNullable(calendar.getTasks()).map(it -> it.stream().map(CalendarItem::fromTask).collect(toList())).orElse(emptyList()));
// workOrders
calendarItems.addAll(Optional.ofNullable(calendar.getWorkOrders()).map(it -> it.stream().map(CalendarItem::fromWorkOrder).collect(toList())).orElse(emptyList()));
// estimates
calendarItems.addAll(Optional.ofNullable(calendar.getEstimates()).map(it -> it.stream().map(CalendarItem::fromEstimate).collect(toList())).orElse(emptyList()));
// blockTimes
calendarItems.addAll(Optional.ofNullable(calendar.getBlockTimes()).map(it -> it.stream().map(CalendarItem::fromBlockTime).collect(toList())).orElse(emptyList()));
return calendarItems;
})
.observeOn(AndroidSchedulers.mainThread())
.subscribe(calendarItems -> view.displayCalendar(calendarItems), view::handleError);如果你只想使用RxJava，你也可以使用下面的代码。(它看起来有点复杂。)
Disposable disposable = calendarRepository.getCalendar(startDate, endDate)
.subscribeOn(Schedulers.io())
.map(calendar -> {
List<Task> tasks = calendar.getTasks();
List<WorkOrder> workOrders = calendar.getWorkOrders();
List<BlockTime> blockTimes = calendar.getBlockTimes();
List<Estimate> estimates = calendar.getEstimates();
List<CalendarItem> calendarItems = new ArrayList<>();
// tasks
if (tasks != null) {
calendarItems.addAll(
Observable.fromIterable(tasks)
.map(CalendarItem::fromTask)
.toList()
.blockingGet()
);
}
// workOrders
if (workOrders != null) {
calendarItems.addAll(
Observable.fromIterable(workOrders)
.map(CalendarItem::fromWorkOrder)
.toList()
.blockingGet()
);
}
// estimates
if (blockTimes != null) {
calendarItems.addAll(
Observable.fromIterable(estimates)
.map(CalendarItem::fromEstimate)
.toList()
.blockingGet()
);
}
// blockTimes
if (blockTimes != null) {
calendarItems.addAll(
Observable.fromIterable(blockTimes)
.map(CalendarItem::fromBlockTime)
.toList()
.blockingGet()
);
}
return calendarItems;
})
.observeOn(AndroidSchedulers.mainThread())
.subscribe(calendarItems -> view.displayCalendar(calendarItems), view::handleError);Stack Overflow用户
发布于 2018-10-25 05:46:39
一种方法是使用更具功能性的样式，如下所示：
.flatMap(calendar -> {
Observable<CalendarItem> tasks = Observable
.just(Optional.ofNullable(calendar.getTasks()).orElse(Collections.emptyList()))
.map(task -> {
CalendarItem item = new CalendarItem();
item.setType(Constants.CALENDAR_TASK);
item.setTask(task);
return item;
});
Observable<CalendarItem> workOrders = Observable
.just(Optional.ofNullable(calendar.getWorkOrders()).orElse(Collections.emptyList()))
.map(workOrder -> {
CalendarItem item = new CalendarItem();
item.setType(Constants.CALENDAR_WORK_ORDER);
item.setWorkOrder(task);
return item;
});
// estimates and blockTimes
return tasks.mergeWith(workOrders).mergeWith(estimates).mergeWith(blockTimes);
});页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/52977918
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