RxJava in Baby Steps

Reactive Programming with RxJava has widely been adopted by both backend services and Android applications alike. Yet, the steep learning curve leaves many developers hesitant about adding it to their own Software tool belt. I was one such developer. Over the past two years, I’ve watched countless videos, read numerous blog posts and attended several conference talks on the subject. Yet, I often left each experience feeling only slightly more knowledgeable, but not quite empowered to start using RxJava in my apps. That’s not going to happen in this talk!

We cover the bare minimum concepts you need to grok, in order to start using RxJava today. In particular, we focus on:
* The 3 O’s: Observable, Observer and Operator
* The most common Operators: map(), flatMap(), and filter()
* Understanding those Marble Diagrams

Transcript

2. a learning curve
3. a steep learning curve
4. you a steep learning curve
5. superstar a steep learning curve you
6. you superstar a steep learning curve
7. you superstar a steep learning curve me
8. RxJava in baby steps @brwngrldev
9. asynchronous data streams
11. GPS Updates Time
12. GPS Updates Time -36.34543, 3.23445
13. -36.34543, 3.23445 -36.24543, 3.23425 GPS Updates Time
14. -36.34543, 3.23445 -36.24543, 3.23425 -35.34543, 3.13445 GPS Updates Time
15. Time server response
16. i want toys!!! Time server response
17. Time server response toys
18. Time i want toys!!! server response
19. Time server response
20. Which of the following is an asynchronous data stream? A: click events B: database access C: server response D: all of the above
21. A: click events B: database access C: server response D: all of the above Which of the following is an asynchronous data stream?
25. scientific Research
26. scientific Research
29. Data Transformati on Observable.just(5, 6, 7) .map { ";-) ".repeat(it) } .subscribe { println(it) }
30. Data Transformati on Observable.just(5, 6, 7) .map { ";-) ".repeat(it) } .subscribe { println(it) } ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-)
31. chaining Observable.just(5, 6, 7) .map { ";-) ".repeat(it) } .filter { it.length < 24 } .subscribe { println(it) }
32. chaining ;-) ;-) ;-) ;-) ;-) Observable.just(5, 6, 7) .map { ";-) ".repeat(it) } .filter { it.length < 24 } .subscribe { println(it) }
35. RxJava is. . . ? A: the silver bullet B: simply magic C: pure voodoo D: a library
36. RxJava is. . . ? A: the silver bullet B: simply magic C: pure voodoo D: a library
37. listOf(5, 6, 7) .map { it * 5 } .filter { it > 25 } kotlin collecti ons
38. listOf(5, 6, 7) .map { it * 5 } .filter { it > 25 } kotlin collecti ons 5 6 7
39. listOf(5, 6, 7) .map { it * 5 } .filter { it > 25 } kotlin collecti ons 5 6 7 map 25 30 35
40. listOf(5, 6, 7) .map { it * 5 } .filter { it > 25 } kotlin collecti ons 5 6 7 map 25 30 35 filter 30 35
42. listOf(5, 6, 7) .asSequence() .map { it * 5 } .filter { it > 25 } .toList() kotlin sequences
43. kotlin sequences listOf(5, 6, 7) .asSequence() .map { it * 5 } .filter { it > 25 } .toList() 5 6 7
44. 5 6 7 map filter kotlin sequences 25 listOf(5, 6, 7) .asSequence() .map { it * 5 } .filter { it > 25 } .toList()
45. 5 6 7 map filter kotlin sequences 25 30 30 listOf(5, 6, 7) .asSequence() .map { it * 5 } .filter { it > 25 } .toList()
46. 5 6 7 map filter kotlin sequences 25 30 35 30 35 listOf(5, 6, 7) .asSequence() .map { it * 5 } .filter { it > 25 } .toList()
48. asynchronous data streams
49. RxJava numbers .map { it * 5 } .filter { it > 25 } .subscribe()
50. RxJava numbers .map { it * 5 } .filter { it > 25 } .subscribe() 5 25 map filter
51. RxJava numbers .map { it * 5 } .filter { it > 25 } .subscribe() 5 6 map filter 25 30 30
52. RxJava numbers .map { it * 5 } .filter { it > 25 } .subscribe() 5 6 map filter 25 30 30 35 7 35 35
53. flexible threading
54. schedulers
55. Observable.just(5, 6, 7) .map { ";-) ".repeat(it) } .subscribe { println(it) }
56. Observable.just(5, 6, 7) .subscribeOn(Schedulers.io()) .map { ";-) ".repeat(it) } .subscribe { println(it) }
58. The Basics observable
59. The Basics observable observer
60. The Basics operators observable observer
61. observable
63. hot observable Time
64. hot observable Time i want hugs!!!
65. hot observable Time hugs
66. hot observable Time hugs hugs
67. hot observable Time hugs hugs hugs
69. Cold observable Time
70. Cold observable Time
71. Cold observable Time
72. Cold observable Time hugs
73. Cold observable Time hugs hugs
74. Cold observable Time hugs hugs hugs
76. where?
77. Observable.create<Int> { subscriber -> }
78. Observable.create<Int> { subscriber -> } Observable.just(item1, item2, item3)
79. Observable.create<Int> { subscriber -> } Observable.just(item1, item2, item3) Observable.interval(2, TimeUnit.SECONDS)
80. Observable.create<Int> { subscriber -> }
81. Observable.create<Int> { subscriber -> Logger.log("create") Logger.log("complete") } Logger.log("done")
82. Observable.create<Int> { subscriber -> Logger.log("create") subscriber.onNext(5) subscriber.onNext(6) subscriber.onNext(7) Logger.log("complete") } Logger.log("done")
83. Observable.create<Int> { subscriber -> Logger.log("create") subscriber.onNext(5) subscriber.onNext(6) subscriber.onNext(7) subscriber.onComplete() Logger.log("complete") } Logger.log("done")
86. A: emit items B: be cold C: be hot D: all of the above Observables can. . .
87. A: emit items B: be cold C: be hot D: all of the above Observables can. . .
88. observer
89. interface Observer<T> { fun onError(e: Throwable) fun onComplete() fun onNext(t: T) fun onSubscribe(d: Disposable) }
90. interface Observer<T> { fun onError(e: Throwable) fun onComplete() fun onNext(t: T) fun onSubscribe(d: Disposable) }
91. interface Observer<T> { fun onError(e: Throwable) fun onComplete() fun onNext(t: T) fun onSubscribe(d: Disposable) }
92. interface Observer<T> { fun onError(e: Throwable) fun onComplete() fun onNext(t: T) fun onSubscribe(d: Disposable) }
93. interface Observer<T> { fun onError(e: Throwable) fun onComplete() fun onNext(t: T) fun onSubscribe(d: Disposable) }
94. observer’s lifecycle onSubscribe
95. observer’s lifecycle onNext Normal flow onSubscribe
96. observer’s lifecycle onComplete Normal flow onSubscribe onNext
97. observer’s lifecycle onComplete onError Normal flow onSubscribe onNext
98. val observer = object : Observer<Int> { override fun onError(e: Throwable) { Logger.log(e) } override fun onComplete() { Logger.log("on complete") } override fun onNext(t: Int) { Logger.log("next: $t") } override fun onSubscribe(d: Disposable) { Logger.log("on subscribe") } }
100. interface Consumer<T> { fun accept(t: T) }
101. val consumer = object : Consumer<Int> { override fun accept(t: Int) { Logger.log("next: $t") } }
104. val consumer = Consumer<Int> { t -> Logger.log("next: $t") } obs.subscribe(consumer) consumer
105. obs.subscribe(Consumer<Int> { t -> Logger.log("next: $t") }) consumer
106. obs.subscribe({ t -> Logger.log("next: $t") }) consumer
107. obs.subscribe{ t -> Logger.log("next: $t") } consumer
108. obs.subscribe{ Logger.log("next: $it") } consumer
110. A: have a lifecycle B: always complete C: Never Error D: all of the above Observers. . .
111. Observers. . . A: have a lifecycle B: always complete C: Never Error D: all of the above
112. operator
113. Time Operator: map()
114. Time Operator: map() :-) :-(
115. Time Operator: map() :-) :-) :-( :-(
116. Time Operator: map() :-) :-) :-) :-( :-( :-(
117. Time Operator: map() :-) :-) :-) :-) :-( :-( :-( :-(
118. Operator: map() Observable.just(5, 6, 7) .map { ";-) ".repeat(it) } .subscribe { println(it) }
119. Operator: map() ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) ;-) Observable.just(5, 6, 7) .map { ";-) ".repeat(it) } .subscribe { println(it) }
120. Operator: map() Observable.just(5, 6, 7) .map(object: Function<Int, String> { override fun apply(t: Int): String { return ";-) ".repeat(t) } }) .subscribe { println(it) }
121. Operator: map() Observable.just(5, 6, 7) .map(object: Function<Int, String> { override fun apply(t: Int): String { return ";-) ".repeat(t) } }) .subscribe { println(it) }
122. Operator: map() Observable.just(5, 6, 7) .map(object: Function<Int, String> { override fun apply(t: Int): String { return ";-) ".repeat(t) } }) .subscribe { println(it) }
123. Operator: map() Observable.just(5, 6, 7) .map(object: Function<Int, String> { override fun apply(t: Int): String { return ";-) ".repeat(t) } }) .subscribe { println(it) }
124. .map(object: Function<Int, String> { override fun apply(t: Int): String { return ";-) ".repeat(t) } }) .map { ";-) ".repeat(it) }
126. what’s the output? Observable.just(1, 2, 3) .map { it * 2 } .subscribe { println(it) }
127. A: 1, 2, 3 B: a, b, c C: 2, 4, 6 D: 6, 2, 4 Observable.just(1, 2, 3) .map { it * 2 } .subscribe { println(it) } what’s the output?
128. Observable.just(1, 2, 3) .map { it * 2 } .subscribe { println(it) } A: 1, 2, 3 B: a, b, c C: 2, 4, 6 D: 6, 2, 4 what’s the output?
129. what’s the output? Observable.just(1, 2, 3) .map { it * 2 } .filter { it < 6 } .subscribe { println(it) }
130. A: 2, 3, 1 B: 2, 4 C: 1, 2, 3 D: 6, 4 what’s the output? Observable.just(1, 2, 3) .map { it * 2 } .filter { it < 6 } .subscribe { println(it) }
131. what’s the output? Observable.just(1, 2, 3) .map { it * 2 } .filter { it < 6 } .subscribe { println(it) } A: 2, 3, 1 B: 2, 4 C: 1, 2, 3 D: 6, 4
132. Operator: flatmap() via reactivex.io
133. Operator: flatmap() via reactivex.io item
134. Operator: flatmap() via reactivex.io item observable
135. Operator: flatmap() Observable.just( , ) .flatMap( { Observable.just( ) } ) .subscribe { println(it) } :-( :-(
136. time flatmap
137. time flatmap :-(
138. time flatmap :-(
139. time flatmap :-(
140. time flatmap :-( :-(
141. time flatmap :-( :-(
142. time flatmap :-( :-(
143. time flatmap :-( :-(
144. Long Running asynchronous
145. Operator: flatmap() val users // Observable<User>
146. Operator: flatmap() val users // Observable<User> val posts: Observable<Post>
147. Operator: flatmap() val users // Observable<User> val posts: Observable<Post> posts = users.flatMap { getUsersPosts(it.id) }
148. Operator: flatmap() val users // Observable<User> val posts: Observable<Post> posts = users.flatMap { getUsersPosts(it.id) } posts.subscribe { println(it) }
149. via reactivex.io
150. Flowable Maybe backpressure Disposable Single completable
151. should you use rxjava?
152. like functi onal programing? Process items asynchronously? compose data? handle errors gracefully? should you use rxjava?
153. should you use rxjava? like functi onal programing? Process items asynchronously? compose data? handle errors gracefully?
154. it depends
155. The Basics operators observable observer
156. you
157. www.adavis.info @brwngrldev
158. • Reactive Programming on Android with RxJava (http://amzn.to/2yOAkxn) • Reactive Programming with RxJava (http://amzn.to/2zQtqb5) • RxJava Playlist (https://goo.gl/9fw1Zv) • Learning RxJava for Android Devs (https://goo.gl/VWxFLK) • RxJava Video Course (https://caster.io/courses/rxjava) resources
159. slide design: @lauraemilyillustrati on font: Elli ot 6, fontSquirrel.com