装饰可观察

Question

Is it OK to decorate Observable<> , Single<> , Maybe<> , Flowable<> in rx-java?
Eg like this:

public final class NonEmptyStringSource extends Observable<String> {

    private final Observable<String> source;

    public NonEmptyStringSource(final Observable<String> source) {
        this.source = source.filter(s -> s.length() > 0);
    }

    @Override
    protected void subscribeActual(final Observer<? super String> observer) {
        this.source.subscribe(observer);
    }
}

Does this approach have some pitfalls?
Is it safe in use?

Answer 1

Unlike 1.x, this pattern in 2.x has no penalty and is almost like how the standard operators are implemented. Depending on your needs, you may want to implement an ObservableTransformer instead:

ObservableTransformer<String, String> t = 
    upstream -> upstream.filter(s -> s.length() > 0);

Observable.fromArray("a", "b", "", "d", "", "f")
.compose(t)
.subscribe(System.out::println, Throwable::printStackTrace);

Answer 2

I would advise against this, as it just obfuscates what is actually going on.

Just using filter inline is cleaner and more readable:

 .filter(StringUtils::isNotBlank)

This comes from Apache Commons-Lang, but you can roll your own implementation just as easily.