CODEWITHSUNDEEP
androidrx-javarx-java2
Efe Budak
Efe Budak

Reputation: 659

How to convert Map<String, Spending> object to `Observable<List<Spendings>>` on rxjava2?

I am trying to migrate rxjava to rxjava2. 

Map<String, Task> mCachedTasks;

I can convert it to Observable<List<Task>> by using the following line of code. Observable.from(mCachedTasks.values()).toList()

However, I cannot convert it on rxjava2. 1- I tried the following code. Observable.fromIterable(mCachedTasks.values()) but it returns Observable<Task>

2- I also tried to use fromArray method, such as Observable.fromArray(mCachedTasks.values().toArray()). That gives me Observable<Object>.

How can I convert Map<String, Task> to Observable<List<Task>> on rxjava2?

Upvotes: 0

Views: 1650

Answers (4)

nyulan
nyulan

Reputation: 321

public Observable> getOrganizations() {

    List<Organization> list=new ArrayList<>(mcached.values());

    if(mcached!=null && !mCacheIsDirty){

        //return your map as list
        return Observable.just(list);

    }else {
        mcached=new LinkedHashMap<>();
    }
}

Upvotes: 0

Yuriy Kulikov
Yuriy Kulikov

Reputation: 2129

Another option is to create a lazy Observable:

Observable<List<Task>> taskListObservable = Observable.fromCallable(
    //this will be called each time someone subscribes
    () -> {
        //do not forget the defensive copy
        return new ArrayList<>(mCachedTasks.values());
    }
);

This way mCachedTasks.values() will always get the fresh version and there will be no unnecessary flattening with toList() operator.

Upvotes: 0

Scott Wang
Scott Wang

Reputation: 498

Observable.fromIterable(mCachedTasks.values()).toList().toObservable();

Upvotes: 0

yosriz
yosriz

Reputation: 10267

I can convert it to Observable> by using the following line of code. Observable.from(mCachedTasks.values()).toList()

That's an option, but you are unnecessarily flatting the list - the from(), you taking a list and emit each item in onNext() , and then collect it back as a list using toList(), which waits for all the emissions and then emit single onNext() with the collected list.

However, I cannot convert it on rxjava2. 1- I tried the following code. Observable.fromIterable(mCachedTasks.values()) but it returns Observable<Task>

fromIterable() it's RxJava2 equivalent to from() of RxJava1, you can use again toList() - but in RxJava2 you will get Single instead of Observable (which is more concise API).

2- I also tried to use fromArray method, such as Observable.fromArray(mCachedTasks.values().toArray()). That gives me Observable<Object>

That's because toArray() return array of Object not Task.

The solution is rather simple, you actually don't need RxJava for the transformation , you've got already an in-memory Map, so first convert it to a List (if you insisting on List specifically):

List<Task> tasksList = new ArrayList<>(mCachedTasks.values());

and then use just() operator to create an Observable that emit this list as it's single value:

Observable<List<Task>> taskListObservable = Observable.just(tasksList);

Upvotes: 2

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