RxJava2 and Dagger2 - Speaker Deck

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Introduction to Reactive Programming and Dagger Kaushal Dhruw @drulabs (twitter, GitHub, medium)

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Contents • MVP brief intro • Reactive programming • Retrofit with RxJava2 • Room with RxJava2 • Dependency injection & Dagger • Putting it all together 2

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. What’s NOT covered x Room x Retrofit x Advanced concepts x Testing x MVP, MVVM from scratch x Step by step walk through x In-depth knowledge of RxJava2 and Dagger2 3

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Reactive Programming

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Reactive programming • Wikipedia – It is an asynchronous programming paradigm concerned with data flows and propagation of change. • In other words: – Reactive programming is programming with asynchronous data streams.

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Reactive Extensions (Rx) • Reactive extensions (or Rx) is a library for composing asynchronous and event-based programs by using observable sequences

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Reactive Extensions (Rx) • Reactive extensions (or Rx) is a library for composing and programs by using sequences simultaneous operations. perform some operation(s) when event is triggered or received. think of it as asynchronous immutable array.

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. RxJava & RxAndroid • RxJava is a Java VM implementation of ReactiveX. • RxAndroid provides android specific bindings and extensions. So RxJava can be used in android applications

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Reactive Programming Components

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Components • Source (emits data) – Emits data streams • Subscriber (the observer or consumer) – Consumes data emitted from source • Scheduler (threads and concurrency) – Where to process and consume data

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Components Source (observable) Subscriber (observer) Scheduler (concurrency) subscribe dispose Time onNext(1) onNext(2) Error / complete onNext(3)

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Source & Subscriber Source (observable) Time onNext(1) onNext(2) Error / complete onNext(3) Subscriber (observer) subscribe dispose

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Schedulers Source (observable) Time Subscriber (observer) Scheduler (concurrency) Thread t = new Thread(…); t.start(); Wait() Notify()

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Schedulers Source (observable) Time Subscriber (observer) Scheduler (concurrency) • io() • computation() • newThread() • from(Executer)

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Source, Subscriber & Scheduler Source (observable) Time onNext(1) onNext(2) Error / complete onNext(3) Subscriber (observer) subscribe dispose Scheduler (concurrency)

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Source • Observable • Flowable • Single • Maybe • Completable • ObservableSource • Publisher • SingleSource • MaybeSource • CompletableSource

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Flowable • Observable • Flowable • Single • Maybe • Completable Emits 0 to N items terminates with success or exception. Supports backpressure

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Maybe • Observable • Flowable • Single • Maybe • Completable Succeeds with 0 or 1 item, or fails. Has completion indicator. Reactive optional.

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. RxJava Operators • Creational – Create – Just – From • Transformational – Map – Flatmap – Group by • Filter – Filter – Distinct – Skip • Combine – Concat – Merge – Zip

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Dependency injection Dagger2

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Dependency injection Got all the ingredients for pizza except the base Should I create pizza base myself? You are gonna mess it up let me do it

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Dependency injection Instead of having hidden dependencies, pass the dependent objects • loose coupling • Testable code • Reusable code • Readable code • Enforces SRP

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Dagger2 Dagger is a compile time dependency injection framework for both Java and Android. I will inject the dependencies just tell me: • What dependencies to inject - @Component • How to create it - @Module, @Provides • Where to inject - @Inject • Which one to inject - @Qualifier, @Named

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Dagger dependency graph Pizza Pizza base Chicken sausage Cheese Flour Chicken Milk salt Processed chicken Toppings Tomato chilli ﬂakes oregano

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Dagger code and demo

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Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved. Summary • Brief introduction of MVP • Reactive programming – What, why and how? – Various operators – With Room and Retrofit • Dagger • How these work together