Rxjava2 map

99

map的作用是把上游的数据转换后再发给下游。

  Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(@NotNull ObservableEmitter<Integer> emitter) throws Exception {
                emitter.onNext(1);
                emitter.onNext(3);
                emitter.onNext(5);
                emitter.onComplete();
            }
        }).map(new Function<Integer, Integer>() {
            @Override
            public Integer apply(@NotNull Integer integer) throws Exception {
                return integer + 1;
            }
        }).subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                System.out.println(integer);
            }
        });
 public final <R> Observable<R> map(Function<? super T, ? extends R> mapper) {
        ...
        return RxJavaPlugins.onAssembly(new ObservableMap<T, R>(this, mapper));
    }
public final class ObservableMap<T, U> extends AbstractObservableWithUpstream<T, U> {
    final Function<? super T, ? extends U> function;

    public ObservableMap(ObservableSource<T> source, Function<? super T, ? extends U> function) {
        super(source);
        this.function = function;
    }

    @Override
    public void subscribeActual(Observer<? super U> t) {
        source.subscribe(new MapObserver<T, U>(t, function));
    }

    static final class MapObserver<T, U> extends BasicFuseableObserver<T, U> {
        final Function<? super T, ? extends U> mapper;

        MapObserver(Observer<? super U> actual, Function<? super T, ? extends U> mapper) {
            super(actual);
            this.mapper = mapper;
        }

        @Override
        public void onNext(T t) {
            if (done) {
                return;
            }

            if (sourceMode != NONE) {
                downstream.onNext(null);
                return;
            }

            U v;

            try {
                //数据转换后交给下游
                v = ObjectHelper.requireNonNull(mapper.apply(t), "The mapper function returned a null value.");
            } catch (Throwable ex) {
                fail(ex);
                return;
            }
            downstream.onNext(v);
        }

        @Override
        public int requestFusion(int mode) {
            return transitiveBoundaryFusion(mode);
        }

        @Nullable
        @Override
        public U poll() throws Exception {
            T t = qd.poll();
            return t != null ? ObjectHelper.<U>requireNonNull(mapper.apply(t), "The mapper function returned a null value.") : null;
        }
    }
}