Rxjava(过滤类)-Filter

只发射通过了谓词测试的数据项

 Observable.range(1, 10).filter(new Func1() {
            @Override
            public Boolean call(Integer integer) {
                return integer % 2 == 0;
            }
        }).subscribe(new Action1() {
            @Override
            public void call(Integer integer) {
                System.out.println(integer);
            }
        });

看一下filter函数

public final Observable filter(Func1 predicate) {
        return create(new OnSubscribeFilter(this, predicate));
    }

   public OnSubscribeFilter(Observable source, Func1 predicate) {
        this.source = source;
        this.predicate = predicate;
    }

predicate就是我们的过滤函数

前面分析可知RangeProducer最终会调用

void fastPath() {
            final long endIndex = this.endOfRange + 1L;
            final Subscriber childSubscriber = this.childSubscriber;
            for (long index = currentIndex; index != endIndex; index++) {
                if (childSubscriber.isUnsubscribed()) {
                    return;
                }
                childSubscriber.onNext((int) index);
            }
            if (!childSubscriber.isUnsubscribed()) {
                childSubscriber.onCompleted();
            }
        }

这里的childSubscriber是FilterSubscriber

 public void onNext(T t) {
            boolean result;

            try {
                result = predicate.call(t);
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                unsubscribe();
                onError(OnErrorThrowable.addValueAsLastCause(ex, t));
                return;
            }

            if (result) {
                actual.onNext(t);
            } else {
                request(1);
            }
        }

调用过滤函数获取过滤结果，如果为true才调用onNext,达到过滤效果