RxJava: How to convert List of objects to List of another objects

Question

I have the List of SourceObjects and I need to convert it to the List of ResultObjects.

I can fetch one object to another using method of ResultObject:

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Answer 1

If you want to maintain the Lists emitted by the source Observable but convert the contents, i.e. Observable> to Observable>, you can do something like this:

Observable> source = ...
source.flatMap(list ->
        Observable.fromIterable(list)
            .map(item -> new ResultsObject().convertFromSource(item))
            .toList()
            .toObservable() // Required for RxJava 2.x
    )
    .subscribe(resultsList -> ...);

This ensures a couple of things:

• The number of Lists emitted by the Observable is maintained. i.e. if the source emits 3 lists, there will be 3 transformed lists on the other end
• Using Observable.fromIterable() will ensure the inner Observable terminates so that toList() can be used