Slide 1
Slide 1 text
Build Your Custom
Observable/Operator
Hiroshi Kurokawa (@hydrakecat)
Slide 2
Slide 2 text
Reference
• The Slides
https://speakerdeck.com/hkurokawa/operator
• RxNearby
https://github.com/hkurokawa/rxnearby
Slide 3
Slide 3 text
When you need custom
Observable/Operator?
// Retrofit
service.users()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(users -> {
adapter.setItems(users);
});
// RxBinding
RxView.scrollChangeEvents(listView)
.subscribe(event -> {
int dy = event.scrollY() - event.oldScrollY();
});
Slide 4
Slide 4 text
When you need custom
Observable/Operator?
// Retrofit
service.users()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(users -> {
adapter.setItems(users);
});
// RxBinding
RxView.scrollChangeEvents(listView)
.subscribe(event -> {
int dy = event.scrollY() - event.oldScrollY();
});
When you want to model something as a stream!
Slide 5
Slide 5 text
When you need custom
Observable/Operator?
// Retrofit
service.users()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(users -> {
adapter.setItems(users);
});
// RxBinding
RxView.scrollChangeEvents(listView)
.subscribe(event -> {
int dy = event.scrollY() - event.oldScrollY();
});
When you want to model something as a stream!
Slide 6
Slide 6 text
When you need custom
Observable/Operator?
// Retrofit
service.users()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(users -> {
adapter.setItems(users);
});
// RxBinding
RxView.scrollChangeEvents(listView)
.subscribe(event -> {
int dy = event.scrollY() - event.oldScrollY();
});
When you want to model something as a stream!
Slide 7
Slide 7 text
When you need custom
Observable/Operator?
// Retrofit
service.users()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(users -> {
adapter.setItems(users);
});
// RxBinding
RxView.scrollChangeEvents(listView)
.subscribe(event -> {
int dy = event.scrollY() - event.oldScrollY();
});
When you want to model something as a stream!
Slide 8
Slide 8 text
(http://slides.com/robwormald/everything-is-a-stream#/)
Slide 9
Slide 9 text
Nearby Messaging API
• Subscribe messages from other Android devices
• Publish messages to other Android devices
Slide 10
Slide 10 text
Nearby Messaging API
• Subscribe messages from other Android devices
Modelled as Observable
• Publish messages to other Android devices
Slide 11
Slide 11 text
Nearby Messaging API
• Subscribe messages from other Android devices
Modelled as Observable
• Publish messages to other Android devices
Modelled as Operator
Operator
Slide 12
Slide 12 text
Nearby Messaging API
• Subscribe messages from other Android devices
Modelled as Observable
• Publish messages to other Android devices
Modelled as Operator
9JCV!1RGTCVQT!
Slide 13
Slide 13 text
Why Operator?
• When and how do you want a message is
published?
- Publish when user clicks a button
- Publish when the app loads data from local
DB or a server
• Why don’t you handle such trigger as an
Observable?
Slide 14
Slide 14 text
(http://slides.com/robwormald/everything-is-a-stream#/)
Slide 15
Slide 15 text
Publishing a message
Trigger Events (ex. button click)
Message Published Events
Operator
Slide 16
Slide 16 text
Publishing a message
Slide 17
Slide 17 text
Publishing a message
Slide 18
Slide 18 text
Publishing a message
Slide 19
Slide 19 text
Publishing a message
Slide 20
Slide 20 text
Publishing a message
Slide 21
Slide 21 text
What is Observable?
What is Operator?
• Observable is something to emit a sequence of events to the
given Subscriber
Slide 22
Slide 22 text
What is Observable?
What is Operator?
• Observable is something to emit a sequence of events to the
given Subscriber
- From implementation points of view, we create an
OnSubscribe instead of Observable itself
Observable.create(new OnSubscribe() { … })
Slide 23
Slide 23 text
What is Observable?
What is Operator?
• Observable is something to emit a sequence of events to the
given Subscriber
- From implementation points of view, we create an
OnSubscribe instead of Observable itself
• Operator converts an Observable to another Observable
Observable.create(new OnSubscribe() { … })
Slide 24
Slide 24 text
What is Observable?
What is Operator?
• Observable is something to emit a sequence of events to the
given Subscriber
- From implementation points of view, we create an
OnSubscribe instead of Observable itself
• Operator converts an Observable to another Observable
- From implementation points of view, we implement a
method to return a subscriber from the given subscriber
Observable.create(new OnSubscribe() { … })
Slide 25
Slide 25 text
What is Observable?
What is Operator?
• Observable is something to emit a sequence of events to the
given Subscriber
- From implementation points of view, we create an
OnSubscribe instead of Observable itself
• Operator converts an Observable to another Observable
- From implementation points of view, we implement a
method to return a subscriber from the given subscriber
Observable.create(new OnSubscribe() { … })
Subscriber is the core of RxJava
Slide 26
Slide 26 text
OnSubscribe Example:
range()
@Override
public void call(Subscriber super Integer> subscriber) {
for (int i = start; i < start + count; i++) {
if (subscriber.isUnsubscribed()) {
return;
}
subscriber.onNext(i);
}
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
Slide 27
Slide 27 text
How OnSubscribe works
Observable.range(1, 5)
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, “Completed.")
);
Slide 28
Slide 28 text
How OnSubscribe works
Observable.range(1, 5)
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, “Completed.")
);
Slide 29
Slide 29 text
How OnSubscribe works
Observable.range(1, 5)
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, “Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
for (int i = start; i < start + count; i++) {
if (subscriber.isUnsubscribed()) {
return;
}
subscriber.onNext(i);
}
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
Slide 30
Slide 30 text
How OnSubscribe works
Observable.range(1, 5)
.subscribe(
i -> Log.i(TAG, "Output: " + 1),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, “Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
for (int i = start; i < start + count; i++) {
if (subscriber.isUnsubscribed()) {
return;
}
subscriber.onNext(1);
}
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
Slide 31
Slide 31 text
How OnSubscribe works
Observable.range(1, 5)
.subscribe(
i -> Log.i(TAG, "Output: " + 2),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, “Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
for (int i = start; i < start + count; i++) {
if (subscriber.isUnsubscribed()) {
return;
}
subscriber.onNext(2);
}
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
Slide 32
Slide 32 text
How OnSubscribe works
Observable.range(1, 5)
.subscribe(
i -> Log.i(TAG, "Output: " + 3),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, “Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
for (int i = start; i < start + count; i++) {
if (subscriber.isUnsubscribed()) {
return;
}
subscriber.onNext(3);
}
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
Slide 33
Slide 33 text
How OnSubscribe works
Observable.range(1, 5)
.subscribe(
i -> Log.i(TAG, "Output: " + 4),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, “Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
for (int i = start; i < start + count; i++) {
if (subscriber.isUnsubscribed()) {
return;
}
subscriber.onNext(4);
}
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
Slide 34
Slide 34 text
How OnSubscribe works
Observable.range(1, 5)
.subscribe(
i -> Log.i(TAG, "Output: " + 5),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, “Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
for (int i = start; i < start + count; i++) {
if (subscriber.isUnsubscribed()) {
return;
}
subscriber.onNext(5);
}
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
Slide 35
Slide 35 text
How OnSubscribe works
Observable.range(1, 5)
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, “Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
for (int i = start; i < start + count; i++) {
if (subscriber.isUnsubscribed()) {
return;
}
subscriber.onNext(i);
}
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
Slide 36
Slide 36 text
Operator Example: map()
@Override
public Subscriber super Integer> call(Subscriber super Integer> child) {
return new Subscriber() {
@Override
public void onCompleted() { child.onCompleted(); }
@Override
public void onError(Throwable e) { child.onError(e); }
@Override
public void onNext(Integer i) {
try {
child.onNext(transformer.call(i));
} catch (Throwable e) {
Exceptions.throwOrReport(e, this, i);
}
}
};
}
Slide 37
Slide 37 text
Operator Example: map()
@Override
public Subscriber super Integer> call(Subscriber super Integer> child) {
return new Subscriber() {
@Override
public void onCompleted() { child.onCompleted(); }
@Override
public void onError(Throwable e) { child.onError(e); }
@Override
public void onNext(Integer i) {
try {
child.onNext(transformer.call(i));
} catch (Throwable e) {
Exceptions.throwOrReport(e, this, i);
}
}
};
}
Slide 38
Slide 38 text
How Operator works
Observable.range(1, 5)
.map(i -> i * 2)
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
Slide 39
Slide 39 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
Slide 40
Slide 40 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
Slide 41
Slide 41 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
Slide 42
Slide 42 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
public final Observable lift(final OperatorMap operator) {
return new Observable<>(new Observable.OnSubscribe() {
@Override
public void call(Subscriber super Integer> o) {
// new Subscriber created and being subscribed with so 'onStart' it
Subscriber super Integer> st = operator.call(o);
st.onStart();
onSubscribe.call(st);
}
});
}
Slide 43
Slide 43 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
public final Observable lift(final OperatorMap operator) {
return new Observable<>(new Observable.OnSubscribe() {
@Override
public void call(Subscriber super Integer> o) {
// new Subscriber created and being subscribed with so 'onStart' it
Subscriber super Integer> st = operator.call(o);
st.onStart();
onSubscribe.call(st);
}
});
}
Slide 44
Slide 44 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
Subscriber super Integer> st = operator.call(o);
st.onStart();
onSubscribe.call(st);
Slide 45
Slide 45 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
Subscriber super Integer> st = operator.call(o);
st.onStart();
onSubscribe.call(st);
child subscriber
Slide 46
Slide 46 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
Subscriber super Integer> st = operator.call(o);
st.onStart();
onSubscribe.call(st);
child subscriber
new subscriber
Slide 47
Slide 47 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
Subscriber super Integer> st = operator.call(o);
st.onStart();
onSubscribe.call(st);
Slide 48
Slide 48 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
Subscriber super Integer> st = operator.call(o);
st.onStart();
onSubscribe.call(st);
Slide 49
Slide 49 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
for (int i = start; i < start + count; i++) {
if (subscriber.isUnsubscribed()) {
return;
}
subscriber.onNext(i);
}
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
Slide 50
Slide 50 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
for (int i = start; i < start + count; i++) {
if (subscriber.isUnsubscribed()) {
return;
}
subscriber.onNext(i);
}
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
Slide 51
Slide 51 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
…
subscriber.onNext(i);
…
}
Slide 52
Slide 52 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
…
subscriber.onNext(i);
…
}
@Override
public void onNext(Integer i) {
child.onNext(transformer.call(i));
}
Slide 53
Slide 53 text
How Operator works
Observable.range(1, 5)
.lift(new OperatorMap(i -> i*2))
.subscribe(
i -> Log.i(TAG, "Output: " + i),
throwable -> Log.e(TAG, "Error: ", throwable),
() -> Log.i(TAG, "Completed.")
);
@Override
public void call(Subscriber super Integer> subscriber) {
…
subscriber.onNext(i);
…
}
@Override
public void onNext(Integer i) {
child.onNext(transformer.call(i));
}
Slide 54
Slide 54 text
How Operator works
• Operator defines how to create a new parent
subscriber from the given child subscriber
• When subscribed, it invokes its onSubscribe with
that new parent subscriber
• When the operators are chained, the onSubscribe
invocations are also chained from child to parent
• The onNext invocations are chained from parent to
child
Slide 55
Slide 55 text
Nearby Messages API
• Subscribe messages from other Android devices
Modelled as Observable
• Publish messages to other Android devices
Modelled as Operator
Slide 56
Slide 56 text
Nearby Messages API
• Subscribe messages from other Android devices
Modelled as Observable
• Publish messages to other Android devices
Modelled as Operator
Slide 57
Slide 57 text
MessageSubscribeOnSubscribe
Nearby.Messages
.subscribe(apiClient, listener)
.setResultCallback(callback);
apiClient.connect();
Slide 58
Slide 58 text
MessageSubscribeOnSubscribe
Nearby.Messages
.subscribe(apiClient, listener)
.setResultCallback(callback);
apiClient.connect();
Slide 59
Slide 59 text
MessageSubscribeOnSubscribe
Nearby.Messages
.subscribe(apiClient, new MessageListener() {
@Override
public void onFound(Message message) {
if (!subscriber.isUnsubscribed()) {
subscriber.onNext(message);
}
}
})
.setResultCallback(callback);
apiClient.connect();
Slide 60
Slide 60 text
MessageSubscribeOnSubscribe
Nearby.Messages
.subscribe(apiClient, new MessageListener() {
@Override
public void onFound(Message message) {
if (!subscriber.isUnsubscribed()) {
subscriber.onNext(message);
}
}
})
.setResultCallback(status -> {
if (!status.isSuccess() && !subscriber.isUnsubscribed()) {
subscriber.onError(new ApiStatusException(status));
}
});
apiClient.connect();
Slide 61
Slide 61 text
MessageSubscribeOnSubscribe
apiClient.unsubscribe(listener, callback);
apiClient.disconnect();
Slide 62
Slide 62 text
subscriber.add(new Subscription() {
@Override
public void unsubscribe() {
}
@Override
public boolean isUnsubscribed() {
return apiClient.isConnected();
}
});
MessageSubscribeOnSubscribe
apiClient.unsubscribe(listener, callback);
apiClient.disconnect();
Slide 63
Slide 63 text
MessageSubscribeOnSubscribe
@Override
public void call(final Subscriber super Message> subscriber) {
final MessageListener listener = new MessageListener() {
@Override
public void onFound(Message message) {
if (!subscriber.isUnsubscribed()) {
subscriber.onNext(message);
}
}
};
final ApiClientWrapper.ResultHandler handler = new ApiClientWrapper.ResultHandler() {
@Override
public void onSuccess() {
}
@Override
public void onError(Status status) {
if (!subscriber.isUnsubscribed()) {
subscriber.onError(new ApiStatusException(status));
}
}
};
apiClient.subscribe(listener, handler);
subscriber.add(new Subscription() {
@Override
public void unsubscribe() {
apiClient.unsubscribe(listener, handler);
apiClient.disconnect();
}
@Override
public boolean isUnsubscribed() {
return apiClient.isConnected();
}
});
apiClient.connect();
}
Slide 64
Slide 64 text
Takeaways
• Basically do not do anything until it is subscribed
• Make sure any resources is released when unsubscribed
• To make it back-pressure aware, use
Subscriber#setProducer()
• The thread of OnSubscribe#call() can be specified with
subscribeOn() operator
• There is a contract. See http://reactivex.io/
documentation/contract.html
Slide 65
Slide 65 text
Nearby Messages API
• Subscribe messages from other Android devices
Modelled as Observable
• Publish messages to other Android devices
Modelled as Operator
Slide 66
Slide 66 text
MessagePublishOperator
@Override
public Subscriber super Message> call(Subscriber super PublishResult> child) {
final ApiClientWrapper apiClient = new ApiClientWrapper(this.context);
return new Subscriber(child) {
@Override
public void onNext(Message message) {
Nearby.Messages.publish(apiClient, message).setResultCallback(status -> {
if (status.isSuccess()) {
child.onNext(new PublishResult(message));
} else {
child.onError(new ApiStatusException(status));
}
});
}
@Override
public void onCompleted() { child.onCompleted(); }
@Override
public void onError(Throwable e) { child.onError(e); }
};
}
Slide 67
Slide 67 text
MessagePublishOperator
@Override
public Subscriber super Message> call(Subscriber super PublishResult> child) {
final ApiClientWrapper apiClient = new ApiClientWrapper(this.context);
return new Subscriber(child) {
@Override
public void onNext(Message message) {
Nearby.Messages.publish(apiClient, message).setResultCallback(status -> {
if (status.isSuccess()) {
child.onNext(new PublishResult(message));
} else {
child.onError(new ApiStatusException(status));
}
});
}
@Override
public void onCompleted() { child.onCompleted(); }
@Override
public void onError(Throwable e) { child.onError(e); }
};
}
Slide 68
Slide 68 text
MessagePublishOperator
final ApiClientWrapper apiClient = new ApiClientWrapper(this.context);
return new Subscriber(child) {
@Override
public void onNext(Message message) {
Nearby.Messages.publish(apiClient,
message).setResultCallback(status -> {
if (status.isSuccess()) {
child.onNext(new PublishResult(message));
} else {
child.onError(new ApiStatusException(status));
}
});
}
};
Slide 69
Slide 69 text
MessagePublishOperator
final ApiClientWrapper apiClient = new ApiClientWrapper(this.context);
return new Subscriber(child) {
@Override
public void onNext(Message message) {
Nearby.Messages.publish(apiClient,
message).setResultCallback(status -> {
if (status.isSuccess()) {
child.onNext(new PublishResult(message));
} else {
child.onError(new ApiStatusException(status));
}
});
}
};
Slide 70
Slide 70 text
MessagePublishOperator
final ApiClientWrapper apiClient = new ApiClientWrapper(this.context);
return new Subscriber(child) {
@Override
public void onNext(Message message) {
Nearby.Messages.publish(apiClient,
message).setResultCallback(status -> {
if (status.isSuccess()) {
child.onNext(new PublishResult(message));
} else {
child.onError(new ApiStatusException(status));
}
});
}
};
Slide 71
Slide 71 text
MessagePublishOperator
final ApiClientWrapper apiClient = new ApiClientWrapper(this.context);
return new Subscriber(child) {
@Override
public void onNext(Message message) {
Nearby.Messages.publish(apiClient,
message).setResultCallback(status -> {
if (status.isSuccess()) {
child.onNext(new PublishResult(message));
} else {
child.onError(new ApiStatusException(status));
}
});
}
};
Slide 72
Slide 72 text
MessagePublishOperator
final ApiClientWrapper apiClient = new ApiClientWrapper(this.context);
return new Subscriber(child) {
@Override
public void onNext(Message message) {
Nearby.Messages.publish(apiClient,
message).setResultCallback(status -> {
if (status.isSuccess()) {
child.onNext(new PublishResult(message));
} else {
child.onError(new ApiStatusException(status));
}
});
}
};
Slide 73
Slide 73 text
MessagePublishOperator
final ApiClientWrapper apiClient = new ApiClientWrapper(this.context);
return new Subscriber(child) {
@Override
public void onNext(Message message) {
Nearby.Messages.publish(apiClient,
message).setResultCallback(status -> {
if (status.isSuccess()) {
child.onNext(new PublishResult(message));
} else {
child.onError(new ApiStatusException(status));
}
});
}
};
Slide 74
Slide 74 text
MessagePublishOperator
@Override
public Subscriber super Message> call(Subscriber super PublishResult> child) {
final ApiClientWrapper apiClient = new ApiClientWrapper(this.context);
return new Subscriber(child) {
@Override
public void onNext(Message message) {
Nearby.Messages.publish(apiClient, message).setResultCallback(status -> {
if (status.isSuccess()) {
child.onNext(new PublishResult(message));
} else {
child.onError(new ApiStatusException(status));
}
});
}
@Override
public void onCompleted() { child.onCompleted(); }
@Override
public void onError(Throwable e) { child.onError(e); }
};
}
Slide 75
Slide 75 text
MessagePublishOperator
@Override
public Subscriber super Message> call(Subscriber super PublishResult> child) {
final ApiClientWrapper apiClient = new ApiClientWrapper(this.context);
return new Subscriber(child) {
@Override
public void onNext(Message message) {
Nearby.Messages.publish(apiClient, message).setResultCallback(status -> {
if (status.isSuccess()) {
child.onNext(new PublishResult(message));
} else {
child.onError(new ApiStatusException(status));
}
});
}
@Override
public void onCompleted() { child.onCompleted(); }
@Override
public void onError(Throwable e) { child.onError(e); }
};
}
Slide 76
Slide 76 text
MessagePublishOperator
@Override
public void onCompleted() { child.onCompleted(); }
@Override
public void onError(Throwable e) { child.onError(e); }
Slide 77
Slide 77 text
MessagePublishOperator
private void init() {
add(new Subscription() {
@Override
public void unsubscribe() {
apiClient.unpublish();
apiClient.disconnect();
}
@Override
public boolean isUnsubscribed() {
return apiClient.isConnected();
}
});
}
Slide 78
Slide 78 text
MessagePublishOperator
private void init() {
add(new Subscription() {
@Override
public void unsubscribe() {
apiClient.unpublish();
apiClient.disconnect();
}
@Override
public boolean isUnsubscribed() {
return apiClient.isConnected();
}
});
}
Slide 79
Slide 79 text
Takeaways
• Call the child subscriber’s onNext()/onError()/onCompleted
appropriately
• Make sure any resources and the newly created parent
subscriber are released when the child subscriber is
unsubscribed
• You can use new Subscriber(Subscriber) to make sure the
subscription and the back-pressure chains
✓ Note, in that case, all the subscriptions are shared with a child subscriber, which may cause
an unexpected behaviour in some cases (See http://akarnokd.blogspot.jp/2015/05/pitfalls-
of-operator-implementations.html)
• Take care of multiple subscriptions
Slide 80
Slide 80 text
Summary
• Subscriber is the core of RxJava
• Custom Observable is pretty easy to create
• Custom Operator is a bit more hard
- Take care of subscriptions and back pressure
• Read “RxJava Advanced”
- Pitfalls of operator implementations (part 1)
http://akarnokd.blogspot.jp/2015/05/pitfalls-of-operator-
implementations.html
Slide 81
Slide 81 text
Thank you!
Hiroshi Kurokawa (ࠇ ༸)
@hydrakecat
https://github.com/hkurokawa
https://speakerdeck.com/hkurokawa
hydrakecat.hatenablog.jp