rxjava1 map操作符分析

rxjava1 map操作符分析

由于源码版本不同，可能会有所差别

代码执行流程分析

create:
创建一个新的Observable

map :
也是创建了一个新的Observable

rx.Observable#create(rx.Observable.OnSubscribe)

OnSubscribe 是create里面的参数

@Deprecated
public static  Observable create(OnSubscribe f) {
    return new Observable(RxJavaHooks.onCreate(f));
}

rx.Observable#map

public final  Observable map(Func1 func) {
	// 这个this是我们通过create方法创建的Observable
    return unsafeCreate(new OnSubscribeMap(this, func));
}

public final class OnSubscribeMap implements OnSubscribe {}	 

rx.Observable#unsafeCreate

OnSubscribe 就是OnSubscribeMap对象，因为它实现了OnSubscribe接口

public static  Observable unsafeCreate(OnSubscribe f) {
	// 这里会修改this这个引用
    return new Observable(RxJavaHooks.onCreate(f));
}

代码调用流程分析

rx.Observable#subscribe(rx.Observer)

public final Subscription subscribe(final Observer observer) {
	// 构建subscribe对象
    return subscribe(new ObserverSubscriber(observer));
}

rx.Observable#subscribe(rx.Subscriber)

this 这个对象是我们上面的Observable对象，即最后一次调用创建的Observable对象，这里是OnSubscribeMap

public final Subscription subscribe(Subscriber subscriber) {
    return Observable.subscribe(subscriber, this);
}	

rx.Observable#subscribe(rx.Subscriber, rx.Observable)

static  Subscription subscribe(Subscriber subscriber, Observable observable) {
	// 这里直接调用了我们上面传入的Observable即OnSubscribeMap的call方法
	RxJavaHooks.onObservableStart(observable, observable.onSubscribe).call(subscriber);
	return RxJavaHooks.onObservableReturn(subscriber);
}

rx.internal.operators.OnSubscribeMap#call

@Override
public void call(final Subscriber o) {
    MapSubscriber parent = new MapSubscriber(o, transformer);
    o.add(parent);
	// source即Observable,即旧的Observable
    source.unsafeSubscribe(parent);
}

rx.Observable#unsafeSubscribe

subscriber OnSubscribeMap$MapSubscriber

public final Subscription unsafeSubscribe(Subscriber subscriber) {
	// 这里调用onSubscribe的call方法,其实就是调用了在create时传入的OnSubscribe的call方法
	// 同把时OnSubscribeMap$MapSubscriber对象的引用作为call方法的参数传入
	// 这样， 在调用subscriber.onNext,onComplete即调用刚才了MapSubscriber中去了
	RxJavaHooks.onObservableStart(this, onSubscribe).call(subscriber);
	return RxJavaHooks.onObservableReturn(subscriber);
}

示例代码

Observable.
	create((Observable.OnSubscribe) subscriber -> {
		LogUtils.loge("OnSubscribe call ... ");
		if (!subscriber.isUnsubscribed()) {
			LogUtils.loge("subscriber.onNext ... ");
			subscriber.onNext("10");
			subscriber.onCompleted();
		}
	}).
	map(s -> {
		return Integer.valueOf(s);
	}).
	subscribe(new Observer() {
		@Override
		public void onCompleted() {
			LogUtils.loge("Observer onCompleted ... ");
		}

		@Override
		public void onError(Throwable e) {

		}

		@Override
		public void onNext(Integer integer) {
			LogUtils.loge("Observer onNext value =  " + integer + " , cls type = " + integer.getClass());
		}
	});  

rx.internal.operators.OnSubscribeMap.MapSubscriber#onNext

@Override
public void onNext(T t) {
	R result;

	// map操作符的func1，即对传入的数据进行转换
	result = mapper.call(t);

	// actual 为ObserverSubscriber,即调用到了Observer的onNext方法
	actual.onNext(result);
}

rx.internal.util.ObserverSubscriber#onNext

@Override
public void onNext(T t) {
	// 调用observer的onNext方法
    observer.onNext(t);
}