The ABCs of RxJava

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The ABCs of RxJavaFlorinaMuntenescu@FMuntenescu

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The ABCs of RxJavaMaking a BurgerFlorinaMuntenescu@FMuntenescu

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Donald Duck’s Burger Joint

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Huey Dewey Louie

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Huey

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Dewey

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Louie

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Huey

Dewey

Louie

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filter(meat -> isMeatFresh(meat))

map(meat -> cook(meat))

Dewey

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zip

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zip

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zip

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zip

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STREAMSOFDATA

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STREAMSOFDATA

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STREAMSOFDATA

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zip

STREAMSOFDATA

18Consumer

Observable

Subscriber

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operators

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Huey.getBun()

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for(Meat meat: meatList){if(!isMeatFresh(meat)){

meatList.remove(meat);}

}

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Observable.from(meatSource).filter(meat ->

isMeatFresh(meat))


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for(Meat meat: meatList){meat = cook(meat);

}

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Observable.from(meatSource).filter(meat ->

isMeatGoneBad(meat)).map(meat -> cook(meat));



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Observable<Burger> burgerObservable = Observable.zip(bunObservable,

meatObservable,tomatoObservable,(bun, meat, tomato) -> makeBurger(bun, meat, tomato))

bunObservable

meatObservable

tomatoObservable

burgerObservable

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Observable<Burger> burgerObservable = Observable.zip(bunObservable,

meatObservable,tomatoObservable,(bun, meat, tomato) -> makeBurger(bun, meat, tomato))

bunObservable

meatObservable

tomatoObservable

burgerObservable

27Consumer

Observable

Subscriber

.subscribe

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Subscriber

burgerObservable.subscribe(mickeySubscriber);

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Subscriber

onNext(Burger burger)

onCompleted()

burgerObservable.subscribe(

burger -> eatBurger(burger),error -> complain(error),() -> leaveBurgerJoint());

//onNext

//onError//onCompleted

onError(Throwable error)

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Observable.zip(bunObservable, meatObservable,tomatoObservable,(bun, meat, tomato) ->

makeBurger(bun, meat, tomato)).subscribe(burger -> eatBurger(burger),

error -> complain(error)); //diningarea

//diningarea

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//kitchen

//diningarea


makeBurger(bun, meat, tomato)).subscribe(burger -> eatBurger(burger),

error -> complain(error));

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//kitchen

//diningarea


makeBurger(bun, meat, tomato)).subscribeOn(kitchen).observeOn(dining area).subscribe(burger -> eatBurger(burger),

error -> complain(error));

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makeBurger(bun, meat, tomato)).subscribeOn(Schedulers.computation()).observeOn(AndroidSchedulers.mainThread()).subscribe(burger -> eatBurger(burger),

error -> complain(error));//diningarea

//kitchen

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Streamofdata

ObservableSubscriber

OperatorsThreads

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Creating Observables

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From a List

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List<Burger> burgers = new ArrayList<>();burgers.add(new Burger());burgers.add(new Burger());

Observable<Burger> burgerObservable = Observable.from(burgers);

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1 2

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burgerObservable.subscribe(new Subscriber<Burger>() {@Overridepublic void onNext(final Burger burger) {

} @Overridepublic void onCompleted() {

}@Overridepublic void onError(final Throwable e) {

}});

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// handle burger 1}@Overridepublic void onCompleted() {


}});

1

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// handle burger 2}@Overridepublic void onCompleted() {


}});

1 2

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}@Overridepublic void onCompleted() {// no more burgers!


}});

1 2

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Observable<List<Burger>>


burgerObservable =Observable.just(burgers);

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1

Observable<List<Burger>> burgerObservable =

Observable.just(burgers);


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Observable<List<Burger>> burgerObservable = Observable.just(burgers);

burgerObservable.subscribe(new Subscriber<List<Burger>>() {

@Overridepublic void onNext(final List<Burger> burgers) {} @Overridepublic void onCompleted() {}@Overridepublic void onError(final Throwable e) {}

});

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burgerObservable.subscribe(new Subscriber<List<Burger>>() {@Overridepublic void onNext(

final List<Burger> burgers) {// handle the list of burgers

} @Overridepublic void onCompleted() {}@Overridepublic void onError(final Throwable e) {}

});

1

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burgerObservable.subscribe(new Subscriber<List<Burger>>() {

@Overridepublic void onNext(

final List<Burger> burgers) {// handle the list of burgers

} @Overridepublic void onCompleted() {// no more burgers!


}});

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From Click Events

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[click!] [click!] [click!]

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???.subscribe(new Subscriber<String>() {

@Overridepublic void onNext(final String s) {

// called on every click}

@Overridepublic void onCompleted() {

}

@Overridepublic void onError(final Throwable e) {

}});

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[click!] [click!] [click!]

???.onNext(…) ???.onNext(…) ???.onNext(…)

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burgerButton.setOnClickListener(new View.OnClickListener() {

@Overridepublic void onClick(final View view) {

}});

PublishSubject<String> burgerRequestedSubject = PublishSubject.create();

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burgerButton.setOnClickListener(new View.OnClickListener() {

@Overridepublic void onClick(final View view) {

burgerRequestedSubject.onNext(…);}

});

PublishSubject<String> burgerRequestedSubject = PublishSubject.create();

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burgerRequestedSubject.subscribe(new Subscriber<String>() {

@Overridepublic void onNext(final String s) {

// called on every click}

@Overridepublic void onCompleted() {

// will never be called for click events}

@Overridepublic void onError(final Throwable e) {

}});

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From Declarative Code

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public Burger cook(){// cooking is time consumingreturn burger;

}

Observable<Burger>burgerObservable =Observable.fromCallable(this::cook);

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Error Handling

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Thread t = new Thread(new Runnable() {@Overridepublic void run() {

cook();}

});

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Thread t = new Thread(new Runnable() {@Overridepublic void run() {try{

cook();} catch(Exception e) {

// handle exception}}

});

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getMeatObservable().filter(meat -> isMeatFresh(meat)).map(meat -> cook(meat)).subscribeOn(

meat -> doSomething(),error -> complain(error));

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getMeatObservable().filter(meat -> isMeatFresh(meat)).map(meat -> cook(meat)).subscribeOn(

meat -> doSomething(),error -> complain(error));

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public Observable<Meat> getCookedMeat() {return getMeatObservable()

.filter(meat -> isMeatFresh(meat))

.map(meat -> cook(meat));}

Observable.zip(getBun(),getCookedMeat(),getTomatoSlice(),(bun, meat, tomato) -> makeBurger(bun, meat, tomato))

.subscribeOn(burger -> eatBurger(burger),error -> complain(error));

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public Observable<Meat> getCookedMeat() {return getMeatObservable()

.filter(meat -> isMeatFresh(meat))

.map(meat -> cook(meat));}

Observable.zip(getBun(),getCookedMeat(),getTomatoSlice(),(bun, meat, tomato) -> makeBurger(bun, meat, tomato))

.subscribeOn(burger -> eatBurger(burger),error -> complain(error));

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Start using RxJava

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public Burger cook(){// cooking is time consuming// make sure it’s on a background threadreturn burger;

}

Observable<Burger> burgerObservable = Observable.fromCallable(this::cook)

.subscribeOn(Schedulers.computation())

.observeOn(AndroidSchedulers.mainThread())

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@GET(“repos”) Call<List<Burger>> repoBurgers();

@GET(“repos”) Observable<List<Burger>> repoBurgers();

7171

The ABCs of RxJava

@FMuntenescu

[email protected]

Building a Reactive Mindsethttps://upday.github.io/blog/reactive_mindset_burgers

Reactive Burgers – Code Example https://github.com/florina-muntenescu/ReactiveBurgers

The ABCs of RxJava

Software

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