寻找一种处理RxJava中错误的干净方法

Question

I'm learning RxJava and I have seen in many places that an error can be handled this way:

repository.getById(10).subscribe(new Action1<User>() {
            @Override
            public void call(User user) {
              //Do something
            }
        }, new Action1<Throwable>() {
            @Override
            public void call(Throwable t) {
                if (t instanceof FirstErrorException) {
                    handleFirstError((FirstErrorException) t);
                } else if (t instanceof FirstErrorException) {
                    handleSecondError((SecondErrorException) t);
                } else {
                    //and so on... 
                }
            }
        });

Am I the only one that thinks that this is really bad code? How can I make it better? I though using Visitor pattern that "visits" each concrete type of my base exception, but onError method always requires an Action1<Throwable> ; you can't use your own base exception, just Throwable .

Answer 1

Error handlers to the rescue:

 <T,E extends Throwable> Observable<T>
 whenExceptionIs(Class<E> what, Func1<E,Observable<T>> result) {
     return t -> {
        return what.isInstance(t) ? result.call(t) : Observable.error(t);
     };
 }

This you use like this:

Observable<Foo> obs = ...
    .onErrorResumeNext(whenExceptionIs(IllegalArgumentException.class, t-> Observable.just(Foo.newInstance())))
    .onErrorResumeNext(whenExceptionIs(IOException.class, t-> Observable.error(new XyzzyException("",t))))
 ....