转换清单 <Object> 列出 <Map> 使用RxJava使用2个键

Question

I have a list of objects and I want to convert it to a list of maps that have a 2 keys.

code example

// list of books (objects)
List<Book> books = new ArrayList<>();
books.add(new Book(1, 6));
books.add(new Book(2, 2));
books.add(new Book(3, 9));
books.add(new Book(4, 18));

List<Map<String, Object>> booksMap = Collections.emptyList();

// convert list into list of maps using regular for-loop
// map structure with 2 keys
for (Book book : books) {
    Map<String, Object> map = new HashMap<>();
    map.put("id", book.getId());
    map.put("quantity", book.getQuantity());

    booksMap.add(map);
}

So each object (book) have to be converted to a Map which hold a 2 keys.

My question is how to do it using RxJava

Answer 1

So you want to subscribe to an Observable created with the fromIterable convenience method which receives your list of books, afterwards it will emit the items one by one, then every item transformed into a Map and finally group them up in a list using the toList operator.

    Observable.fromIterable(books)
    .map(new Function<Book, Map<String, Object>>() {
        @Override
        public Map<String, Object> apply(Book book) throws Exception {
            Map<String, Object> map = new HashMap<String, Object>();
            map.put("id", book.id);
            map.put("quantity", book.quantity);
            return map;
        }
    })
    .toList()
    .subscribe(new Consumer<List<Map<String, Object>>>() {
        @Override
        public void accept(List<Map<String, Object>> mapsList) throws Exception {
            System.out.println(mapsList);
        }
    });