Can you explain the purpose and operation of the switchMap operator in the RxJava library?

The switchMap operator in RxJava is used to transform items emitted by the source Observable into a new Observable and switch to it, canceling the subscription to the previous inner Observable. This is especially useful when working with streams where data relevance is important, such as in search queries where each new request cancels the previous one.

Example: a user types text, and for each change, a server request is initiated. switchMap ensures that only the result from the latest request is processed, and previous requests are canceled.

Observable<String> searchQueryObservable = ...;
searchQueryObservable
    .switchMap(query -> api.search(query)) // api.search returns an Observable<Result>
    .subscribe(result -> {
        // process the result of the latest request
    });

Thus, switchMap helps avoid race conditions and outdated data by switching to a new stream and unsubscribing from the old one.