Kotlin Workshop day #2

Android Academy TLV - Kotlin workshop day #2

Co-created with
Eden Bugdary Machluf and Hadas Peled

Transcript

1. by Hadas Peled Gil Goldzweig Eden Machluf 16/10/19 WIFI: Guest Password: BrokenWires@@2019 1
2. ▢ Workspace + git ▢ Kotlin basics - variables,null safety, conditions, loops, when, ranges. ▢ Functions - syntax, main, filters, lambdas. ▢ Classes - properties, getters & setters, constructors, init, visibility modifiers. 2
3. ▢ More classes: ❏ Inheritance ❏ Abstract ❏ Interfaces ▢ Data class ▢ Special classes ▢ Pairs ▢ Collections ▢ Operators overloading ▢ Constants ▢ Extensions & infix 3
6. class IceCream(var flavor:String="Vanilla",var cone:Boolean=true){ val cup = !cone val base = if(cup) "cup" else "cone" constructor(topping :String): this(){ cone = false } } 6
8. class IceCream(var flavor:String="Vanilla",var cone:Boolean=true){ val cup = !cone val base = if(cup) "cup" else "cone" //.. } 8
9. class IceCream(var flavor:String="Vanilla",var cone:Boolean=true){ val cup = !cone val base = if(cup) "cup" else "cone" //.. } class PizuzIceCream(): IceCream{ //.. } 9
10. class IceCream(var flavor:String="Vanilla",var cone:Boolean=true){ val cup = !cone val base = if(cup) "cup" else "cone" //.. } class PizuzIceCream(): IceCream{ //.. } 10
11. class IceCream(var flavor:String="Vanilla",var cone:Boolean=true){ val cup = !cone val base = if(cup) "cup" else "cone" //.. } class PizuzIceCream(): IceCream{ //.. } 11
12. class IceCream(var flavor:String="Vanilla",var cone:Boolean=true){ val cup = !cone val base = if(cup) "cup" else "cone" //.. } class PizuzIceCream(): IceCream{ //.. } open 12
13. open class IceCream(var flavor:String="Vanilla",var cone:Boolean=true){ val cup = !cone val base = if(cup) "cup" else "cone" //.. } class PizuzIceCream(): IceCream{ override val cup = true //.. } 13
14. open class IceCream(var flavor:String="Vanilla",var cone:Boolean=true){ val cup = !cone val base = if(cup) "cup" else "cone" //.. } open class PizuzIceCream(): IceCream{ override val cup = true addOreos() } 14
15. open class IceCream(var flavor:String="Vanilla",var cone:Boolean=true){ val cup = !cone val base = if(cup) "cup" else "cone" //.. } class PizuzIceCream(): IceCream{ override val cup = true addOreos() } open 15
16. open class IceCream(var flavor:String="Vanilla",var cone:Boolean=true){ open val cup = !cone val base = if(cup) "cup" else "cone" //.. } class PizuzIceCream(): IceCream{ override val cup = true addOreos() } 16
19. abstract class PersonName { abstract val firstName: String } 19
20. abstract class PersonName { abstract val firstName: String } 20
21. abstract class PersonName { abstract val firstName: String val lastName: String = "Shmupidoo" } 21
22. abstract class PersonName { abstract val firstName: String val lastName: String = "Shmupidoo" abstract fun eat() } 22
23. abstract class PersonName { abstract val firstName: String val lastName: String = "Shmupidoo" abstract fun eat() fun drink() { println("drinking") } } 23
24. abstract class PersonName(var nickName: String) { abstract val firstName: String val lastName: String = "Shmupidoo" abstract fun eat() fun drink() { println("drinking") } } 24
25. abstract class PersonName { abstract val firstName: String } 25
26. abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName() { override val firstName: String = name } 26
27. abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName() { override val firstName: String = name } 27
28. abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName() { override val firstName: String = name } 28
29. abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName() { override val firstName: String = name } 29
30. abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName() { override val firstName: String = name } 30
31. abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName() { override val firstName: String = name } 31
32. abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName() { override val firstName: String = name } val person = Person("Rafi") 32
34. interface PersonAction { fun talk(saying: String) } 34
35. interface PersonAction { fun talk(saying: String) } 35
36. interface PersonAction { fun talk(saying: String) } 36
37. interface PersonAction { fun talk(saying: String) } 37
38. interface PersonAction { fun talk(saying: String) val firstName: String } 38
39. interface PersonAction { fun talk(saying: String) val firstName: String val lastName: String = "Shmupidoo" // ?? } 39
40. interface PersonAction { fun talk(saying: String) val firstName: String val lastName: String = "Shmupidoo" } 40
41. interface PersonAction { fun talk(saying: String) val firstName: String val lastName: String get() = "Shmupidoo" } 41
42. interface PersonAction { fun talk(saying: String) val firstName: String val lastName: String get() = "Shmupidoo" fun drink() { println("drinking") } } 42
43. interface PersonAction { fun talk(saying: String) } 43
44. interface PersonAction { fun talk(saying: String) } abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName() { override val firstName: String = name } 44
45. interface PersonAction { fun talk(saying: String) } abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName() { override val firstName: String = name } 45
46. interface PersonAction { fun talk(saying: String) } abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName() { override val firstName: String = name } 46
47. interface PersonAction { fun talk(saying: String) } abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName(), PersonAction { override val firstName: String = name } 47
48. interface PersonAction { fun talk(saying: String) } abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName(), PersonAction { override val firstName: String = name override fun talk(saying: String){ println(saying) } } 48
49. interface PersonAction { fun talk(saying: String) } abstract class PersonName { abstract val firstName: String } class Person(name: String): PersonName(), PersonAction { override val firstName: String = name override fun talk(saying: String){ println(saying) } } 49
51. • Abstract class have constructors • Interface delegation 51
52. • Abstract class have constructors • Interface delegation 52
53. let’s you add features to a class via composition. 53
54. let’s you add features to a class via composition??? 54
55. Is when you use an instance of another class as opposed to inheriting from it. 55
56. let’s you add features to a class while using an instance of another class as opposed to inheriting from it. 56
57. interface Color { val color: String } class JellyBean(): Color { override val color: String = "Red" } object Red: Color { override val color = "Red" } 57
58. interface Color { val color: String } class JellyBean(): Color { override val color: String = "Red" } object Red: Color { override val color = "Red" } 58
59. interface Color { val color: String } class JellyBean(): Color { override val color: String = "Red" } object Red: Color { override val color = "Red" } 59
60. interface Color { val color: String } class JellyBean(): Color { override val color: String = "Red" } object Red: Color { override val color = "Red" } 60
61. interface Color { val color: String } class JellyBean(): Color { override val color: String = "Red" } object Red: Color { override val color = "Red" } 61
62. interface Color { val color: String } class JellyBean(): Color { override val color: String = "Red" } object Red: Color { override val color = "Red" } 62
63. interface Color { val color :String } class JellyBean(): Color { override val color :String = "Red" } object Red: Color { override val color = "Red" } 63
64. interface Color { val color :String } class JellyBean(): Color { override val color :String = "Red" } object Red: Color{ override val color = "Red" } 64
65. interface Color { val color :String } class JellyBean(): Color { override val color :String = "Red" } object Red: Color { override val color = "Red" } 65
66. interface Color { val color :String } class JellyBean(): Color { override val color :String = "Red" } object Red: Color { override val color = "Red" } 66
67. interface Color { val color: String } class JellyBean(): Color { override val color: String = "Red" } object Red: Color { override val color = "Red" } 67
68. interface Color { val color: String } class JellyBean(): Color { override val color: String = "Red" } object Red: Color { override val color = "Red" } 68
69. interface Color { val color: String } class JellyBean(): Color by Red object Red: Color { override val color = "Red" } 69
70. interface Color { val color: String } class JellyBean(): Color by Red object Red: Color { override val color = "Red" } 70
71. interface Color { val color: String } class JellyBean(): Color by Red object Red: Color { override val color = "Red" } val jellyOne = JellyBean() 71
72. interface Color { val color: String } class JellyBean(): Color by Red object Red: Color { override val color = "Red" } val jellyOne = JellyBean() val jellyTwo = JellyBean() 72
73. interface Color { val color: String } class JellyBean(): Color by Red object Red: Color { override val color = "Red" } val jellyOne = JellyBean() val jellyTwo = JellyBean() val jellyThree = JellyBean() 73
74. interface Color { val color: String } class JellyBean(): Color by Red object Red: Color { override val color = "Red" } val jellyOne = JellyBean() val jellyTwo = JellyBean() val jellyThree = JellyBean() 74
76. interface Color { val color: String } class JellyBean(): Color by Red object Red: Color { override val color = "Red" } 76
77. interface Color { val color: String } class JellyBean(jBColor: Color): Color by Red object Red: Color { override val color = "Red" } 77
78. interface Color { val color: String } class JellyBean(jBColor: Color = Red): Color by Red object Red: Color { override val color = "Red" } 78
79. interface Color { val color: String } class JellyBean(jBColor: Color = Red): Color by Red object Red: Color { override val color = "Red" } 79
80. interface Color { val color: String } class JellyBean(jBColor: Color = Red): Color by jBColor object Red: Color { override val color = "Red" } 80
81. interface Color { val color: String } class JellyBean(jBColor: Color = Red): Color by jBColor object Red:Color { override val color = "Red" } 81
82. object Red: Color { override val color = "Red" } object Yellow: Color { override val color = "Yellow" } object Blue: Color { override val color = "Blue" } 82
83. object Red: Color { override val color = "Red" } object Yellow: Color { override val color = "Yellow" } object Blue: Color { override val color = "Blue" } 83
84. object Red: Color { override val color = "Red" } object Yellow: Color { override val color = "Yellow" } object Blue: Color { override val color = "Blue" } 84
85. class JellyBean(jBColor: Color = Red): Color by jBColor 85
86. class JellyBean(jBColor: Color = Red): Color by jBColor val redJelly = JellyBean() 86
87. class JellyBean(jBColor: Color = Red): Color by jBColor val redJelly = JellyBean() val yellowJelly = JellyBean(Yellow) 87
88. class JellyBean(jBColor: Color = Red): Color by jBColor val redJelly = JellyBean() val yellowJelly = JellyBean(Yellow) val blueJelly = JellyBean(Blue) 88
89. WORKSHOP!!! 89
90. class Order(val orderNum: Int, val flavor: String) data 90
91. data class Order(val orderNum: Int, val flavor: String) 91
92. data class Order(val orderNum: Int, val flavor: String){ var name: String = "" } 92
93. data class Order(val orderNum: Int, val flavor: String){ var name: String = "" } 93
94. The compiler automatically derives the following members from all properties declared in the primary constructor: • toString() • componentN() functions • equals() / hashCode() pair • copy() function 94
95. val firstOrder = Order(1, "Vanilla") println(myOrder) // Order(orderNum=1, flavor=Vanilla) 95
96. val firstOrder = Order(1, "Vanilla") println(myOrder) // Order(orderNum=1, flavor=Vanilla) 96
97. val firstOrder = Order(1, "Vanilla") println(myOrder) // Order(orderNum=1, flavor=Vanilla) 97
98. val firstOrder = Order(1, "Vanilla") println(myOrder) // Order(orderNum=1, flavor=Vanilla) 98
99. val firstOrder = Order(1, "Vanilla") println(myOrder) // Order(orderNum=1, flavor=Vanilla) 99
100. val myOrder = Order(1, "Vanilla") val orderNum = myOrder.component1() val flavor = myOrder.component2() 100
101. val myOrder = Order(1, "Vanilla") val orderNum = myOrder.component1() // orderNum: Int = 1 val flavor = myOrder.component2() 101
102. val myOrder = Order(1, "Vanilla") val orderNum = myOrder.component1() val flavor = myOrder.component2() // flavor: String = Vanilla 102
103. val myOrder = Order(1, "Vanilla") val orderNum = myOrder.component1() val flavor = myOrder.component2() 103
104. val firstOrder = Order(1, "Vanilla") firstOrder.name = "Hadas" val secondOrder = Order(1, "Vanilla") secondOrder.name = "Gil" 104
105. val firstOrder = Order(1, "Vanilla") firstOrder.name = "Hadas" val secondOrder = Order(1, "Vanilla") secondOrder.name = "Gil" 105
106. val firstOrder = Order(1, "Vanilla") firstOrder.name = "Hadas" val secondOrder = Order(1, "Vanilla") secondOrder.name = "Gil" 106
107. val firstOrder = Order(1, "Vanilla") firstOrder.name = "Hadas" val secondOrder = Order(1, "Vanilla") secondOrder.name = "Gil" 107
108. val firstOrder = Order(1, "Vanilla") firstOrder.name = "Hadas" val secondOrder = Order(1, "Vanilla") secondOrder.name = "Gil" println( firstOrder.equals(secondOrder) ) 108
109. val firstOrder = Order(1, "Vanilla") firstOrder.name = "Hadas" val secondOrder = Order(1, "Vanilla") secondOrder.name = "Gil" println( firstOrder.equals(secondOrder) )// true or false ?? 109
110. val firstOrder = Order(1, "Vanilla") firstOrder.name = "Hadas" val secondOrder = Order(1, "Vanilla") secondOrder.name = "Gil" println( firstOrder.equals(secondOrder) )// true or false ?? 110
111. val myOrder = Order(1, "Vanilla") 111
112. val myOrder = Order(1, "Vanilla") val newOrder = myOrder.copy() 112
113. val myOrder = Order(1, "Vanilla") val newOrder = myOrder.copy() 113
114. val myOrder = Order(1, "Vanilla") val newOrder = myOrder.copy() 114
115. val myOrder = Order(1, "Vanilla") val brandNewOrder = myOrder.copy(flavor = "Caramel") 115
116. val myOrder = Order(1, "Vanilla") val brandNewOrder = myOrder.copy(flavor = "Caramel") 116
117. val myOrder = Order(1, "Vanilla") val brandNewOrder = myOrder.copy(flavor = "Caramel") println(myOrder) println(brandNewOrder) //Order(orderNum=1, flavor=Vanilla) //Order(orderNum=1, flavor=Caramel) 117
118. val myOrder = Order(1, "Chocolate") val (orderNum, flavor) = myOrder println("The best order is #$orderNum, I love $flavor") //The best order is #1, I love Chocolate 118
119. val myOrder = Order(1, "Chocolate") val (orderNum, flavor) = myOrder println("The best order is #$orderNum, I love $flavor") //The best order is #1, I love Chocolate 119
120. val myOrder = Order(1, "Chocolate") val (orderNum, flavor) = myOrder println("The best order is #$orderNum, I love $flavor") //The best order is #1, I love Chocolate 120
121. val myOrder = Order(1, "Chocolate") val (orderNum, flavor) = myOrder println("The best order is #$orderNum, I love $flavor") //The best order is #1, I love Chocolate 121
122. • The primary constructor needs to have at least one parameter • All primary constructor parameters need to be marked as val or var • Data classes cannot be abstract, open, sealed or inner 122
125. object Configuration { } 125
126. object Configuration { } 126
127. object Configuration { fun registerDataProvider() { /** */ } } 127
128. object Configuration { fun registerDataProvider() { /** */ } } Configuration.registerDataProvider(...) 128
129. object Configuration { fun registerDataProvider() { /** */ } } Configuration.registerDataProvider(...) Called directly 129
130. • Objects are thread safe • Objects are lazily initialized • Functions and variables inside are called directly, just like static 130
132. enum class Direction { NORTH, SOUTH, WEST, EAST } 132
133. enum class Direction { NORTH, SOUTH, WEST, EAST } enum class Color(val rgb: Int) { RED(0xFF0000), GREEN(0x00FF00), BLUE(0x0000FF) } 133
134. enum class Toppings { CHOCOLATE, STRAWBERRY, CARAMEL, BLOOD } 134
135. enum class Toppings { CHOCOLATE, STRAWBERRY, CARAMEL, BLOOD //for the vampires among us } 135
136. fun printBestSource(topping: Toppings) { when (topping) { Toppings.CHOCOLATE -> println("Melting Chocolate") Toppings.STRAWBERRY -> println("From fruit") Toppings.CARAMEL -> println("Hershey's Caramel Syrup") Toppings.BLOOD -> println("Humans?") } } 136
137. enum class Loggers { INFO, DEBUG, ERROR } 137
138. fun log(logger: Loggers, data: Any) { } 138
139. fun log(logger: Loggers, data: Any) { when (logger) { } } 139
140. fun log(logger: Loggers, data: Any) { when (logger) { Loggers.INFO -> println("INFO: $data") } } 140
141. fun log(logger: Loggers, data: Any) { when (logger) { Loggers.INFO -> println("INFO: $data") Loggers.DEBUG -> println("DEBUG: $data") } } 141
142. fun log(logger: Loggers, data: Any) { when (logger) { Loggers.INFO -> println("INFO: $data") Loggers.DEBUG -> println("DEBUG: $data") Loggers.ERROR -> println("ERROR: $data") } } 142
143. fun main() { log( , ) } 143
144. fun main() { log(Loggers.INFO, ) } 144
145. fun main() { log(Loggers.INFO, "me!!!") } 145
146. fun main() { log(Loggers.INFO, "me!!!") // prints -> INFO: me!!! } 146
148. interface Logger { fun log(data: Any) } 148
149. interface Logger { fun log(data: Any) } enum class Loggers { } 149
150. interface Logger { fun log(data: Any) } enum class Loggers : Logger { } 150
151. interface Logger { fun log(data: Any) } enum class Loggers : Logger { INFO, DEBUG, ERROR } 151
152. interface Logger { fun log(data: Any) } enum class Loggers : Logger { INFO { override fun log(data: Any) = print("INFO: $data") }, DEBUG, ERROR } 152
153. interface Logger { fun log(data: Any) } enum class Loggers : Logger { INFO { override fun log(data: Any) = print("INFO: $data") }, DEBUG { override fun log(data: Any) = print("DEBUG: $data") }, ERROR } 153
154. interface Logger { fun log(data: Any) } enum class Loggers : Logger { INFO { override fun log(data: Any) = print("INFO: $data") }, DEBUG { override fun log(data: Any) = print("DEBUG: $data") }, ERROR { override fun log(data: Any) = print("ERROR: $data") } } 154
155. interface Logger { fun log(data: Any) } enum class Loggers : Logger { INFO { override fun log(data: Any) = print("INFO: $data") }, DEBUG { override fun log(data: Any) = print("DEBUG: $data") }, ERROR { override fun log(data: Any) = print("ERROR: $data") } } 155
156. interface Logger … enum class Loggers : Logger … 156
157. interface Logger … enum class Loggers : Logger … fun main() { Loggers.INFO.log("me!!!") } 157
158. interface Logger … enum class Loggers : Logger … fun main() { Loggers.INFO.log("me!!!") // prints -> INFO: me!!! } 158
159. sealed class Response class SuccessfulResponse : Response class ErrorResponse : Response 159
160. fun parseResponse(response: Response): String { return when (response) { is SuccessfulResponse -> "Success" is ErrorResponse -> "Error" } } 160
161. package other.file 161
162. package other.file class OtherResponse 162
163. package other.file class OtherResponse : Response 163
164. package other.file class OtherResponse : Response -> Compile error!! 164
165. WORKSHOP!!! 165
167. val sameType = Pair ("I am String", "me too") 167
168. val sameType = Pair ("I am String", "me too") 168
169. val sameType = Pair ("I am String", "me too") 169
170. val sameType = Pair ("I am String", "me too") val withNull = Pair ("I am String", null) 170
171. val sameType = Pair ("I am String", "me too") val withNull = Pair ("I am String", null) val differentType = Pair (10, "I am String") 171
172. val sameType = Pair ("I am String", "me too") val withNull = Pair ("I am String", null) val differentType = Pair (10, "I am String") 172
173. val sameType = Pair ("I am String", "me too") val withNull = Pair ("I am String", null) val differentType = Pair (10, "I am String") 173
174. val sameType = "I am String" to "me too" val withNull = "I am String" to null val differentType = 10 to "I am String" 174
176. data class Pair<out A, out B> : Serializable 176
177. data class Pair<out A, out B> : Serializable 177
179. • By constructor • By componentN • Destructuring declaration 179
180. • By constructor • By componentN • Destructuring declaration 180
181. By constructure Pair(first: A, second: B) 181
182. val breakfast = "cereal" to "milk" By constructure Pair(first: A, second: B) 182
183. val breakfast = "cereal" to "milk" val cereal = breakfast.first By constructure Pair(first: A, second: B) 183
184. val breakfast = "cereal" to "milk" val cereal = breakfast.first By constructure Pair(first: A, second: B) 184
185. val breakfast = "cereal" to "milk" val cereal = breakfast.first val milk = breakfast.second By constructure Pair(first: A, second: B) 185
186. val breakfast = "cereal" to "milk" val cereal = breakfast.first val milk = breakfast.second By constructure Pair(first: A, second: B) 186
187. • By constructor • By componentN • destructuring declaration 187
188. val breakfast = "cereal" to "milk" By componentN 188
189. val breakfast = "cereal" to "milk" val cereal = breakfast.component1() By componentN 189
190. val breakfast = "cereal" to "milk" val cereal = breakfast.component1() By componentN 190
191. val breakfast = "cereal" to "milk" val cereal = breakfast.component1() val milk = breakfast.component2() By componentN 191
192. val breakfast = "cereal" to "milk" val cereal = breakfast.component1() val milk = breakfast.component2() By componentN 192
193. • By constructor • By componentN • Destructuring declaration 193
194. val breakfast = "cereal" to "milk" Destructuring declaration 194
195. Destructuring declaration val breakfast = "cereal" to "milk" val (cerealVal, milkVal) = breakfast 195
196. Destructuring declaration val breakfast = "cereal" to "milk" val (cerealVal, milkVal) = breakfast 196
197. Destructuring declaration val breakfast = "cereal" to "milk" val (cerealVal, milkVal) = breakfast 197
198. val breakfast = "cereal" to "milk" 198
199. val breakfast = "cereal" to "milk" val breakfastString = breakfast.toString() 199
200. val breakfast = "cereal" to "milk" val breakfastString = breakfast.toString() (cereal, milk) 200
201. val breakfast = "cereal" to "milk" val breakfastString = breakfast.toString() val breakfastList: List<String> = breakfast.toList() 201
202. val breakfast = "cereal" to "milk" val breakfastString = breakfast.toString() val breakfastList: List<String> = breakfast.toList() 202
204. val breakfast = "cereal" to "milk" to "eggs" to "orange juice" 204
205. val breakfast = "cereal" to "milk" to "eggs" to "orange juice" (((cereal, milk), eggs), orange juice) 205
206. val breakfast = "cereal" to "milk" to "eggs" to "orange juice" (((cereal, milk), eggs), orange juice) println(breakfast.first) 206
207. val breakfast = "cereal" to "milk" to "eggs" to "orange juice" (((cereal, milk), eggs), orange juice) println(breakfast.first) ((cereal, milk), eggs) 207
208. val breakfast = "cereal" to "milk" to "eggs" to "orange juice" (((cereal, milk), eggs), orange juice) println(breakfast.first) ((cereal, milk), eggs) breakfast.first 208
209. val breakfast = "cereal" to "milk" to "eggs" to "orange juice" (((cereal, milk), eggs), orange juice) println(breakfast.first) ((cereal, milk), eggs) breakfast.second 209
210. val breakfast = "cereal" to "milk" to "eggs" to "orange juice" (((cereal, milk), eggs), orange juice) println(breakfast.first.second) 210
211. val breakfast = "cereal" to "milk" to "eggs" to "orange juice" (((cereal, milk), eggs), orange juice) println(breakfast.first.second) 211
212. val breakfast = "cereal" to "milk" to "eggs" to "orange juice" breakfast.first 212
213. val breakfast = "cereal" to "milk" to "eggs" to "orange juice" breakfast.first breakfast.first.first 213
214. val breakfast = "cereal" to "milk" to "eggs" to "orange juice" breakfast.first breakfast.first.first breakfast.first.second 214
215. val breakfast = ("cereal" to "milk") to ("eggs" to "orange juice") 215
216. val breakfast = ("cereal" to "milk") to ("eggs" to "orange juice") 216
217. val breakfast = ("cereal" to "milk") to ("eggs" to "orange juice") breakfast.first 217
218. val breakfast = ("cereal" to "milk") to ("eggs" to "orange juice") breakfast.first breakfast.second 218
219. val breakfast = ("cereal" to "milk") to ("eggs" to "orange juice") breakfast.first.second??? breakfast.first breakfast.second 219
220. val breakfast = ("cereal" to "milk") to ("eggs" to "orange juice") breakfast.first 220
221. val breakfast = ("cereal" to "milk") to ("eggs" to "orange juice") breakfast.first breakfast.first.first 221
222. val breakfast = ("cereal" to "milk") to ("eggs" to "orange juice") breakfast.first breakfast.first.first breakfast.first.second 222
224. class IceCream(var flavor: String = "Vanilla",var cone: Boolean = true) 224
225. class IceCream(var flavor: String = "Vanilla",var cone: Boolean = true) fun findBestIceCream 225
226. class IceCream(var flavor: String = "Vanilla",var cone: Boolean = true) fun findBestIceCream(iceCreams: List<IceCream>) 226
227. class IceCream(var flavor: String = "Vanilla",var cone: Boolean = true) fun findBestIceCream(iceCreams: List<IceCream>): IceCream 227
228. class IceCream(var flavor: String = "Vanilla",var cone: Boolean = true) fun findBestIceCream(iceCreams: List<IceCream>): IceCream { val result = IceCream() } 228
229. class IceCream(var flavor: String = "Vanilla",var cone: Boolean = true) fun findBestIceCream(iceCreams: List<IceCream>): IceCream { val result = IceCream() for(iceCream in iceCreams) { // secret algorithm } return result } 229
230. class IceCream(var flavor: String = "Vanilla",var cone: Boolean = true) fun findBestIceCream(iceCreams: List<IceCream>): IceCream { val result = IceCream() for(iceCream in iceCreams) { // secret algorithm } return result } 230
231. class IceCream(var flavor: String = "Vanilla",var cone: Boolean = true) fun findBestIceCream(iceCreams: List<IceCream>): IceCream { val result = IceCream() for(iceCream in iceCreams) { // secret algorithm } return result } 231
232. class IceCream(var flavor: String = "Vanilla",var cone: Boolean = true) fun findBestIceCream(iceCreams: List<IceCream>): IceCream { val result = IceCream() for(iceCream in iceCreams) { // secret algorithm } return result } 232
233. class IceCream(var flavor: String = "Vanilla",var cone: Boolean = true) fun findBestIceCream(iceCreams: List<IceCream>): IceCream { val result = IceCream() var score = 0 for(iceCream in iceCreams) { // secret algorithm } return result } 233
234. class IceCream(var flavor: String = "Vanilla",var cone: Boolean = true) fun findBestIceCream(iceCreams: List<IceCream>): Pair<IceCream, Int> { val result = IceCream() var score = 0 for(iceCream in iceCreams) { // secret algorithm } return result to score } 234
236. • groups of a variable number of items. • The Kotlin Standard Library provides implementations for basic collection types: sets, lists, and maps. • Each type have two options: ◦ A read-only interface. ◦ Mutable interface with write operations. 236
237. val list = listOf(1, 5, 3, 4) 237
238. val list = listOf(1, 5, 3, 4) val mutableList = mutableListOf("an", "d", "ro", "id") 238
239. val list = listOf(1, 5, 2, 4) var sum = 0 for (it in list){ sum = sum+it } println(sum) //12 239
240. val list = listOf(1, 5, 2, 4) println(list.sum()) //12 240
241. val list = listOf(1, 5, 2, 4) println(list.sum()) //12 241
242. val list = listOf(1, 5, 2, 4) println(list.sum()) //12 242
243. val listDroid = listOf("an", "d", "ro", "id") println(listDroid.sum()) 243
244. val listDroid = listOf("an", "d", "ro", "id") println(listDroid.sum()) Error! 244
245. val listDroid = listOf("an", "d", "ro", "id") println(listDroid.sumBy { it.length }) 245
246. val listDroid = listOf("an", "d", "ro", "id") println(listDroid.sumBy { it.length }) 246
247. val listDroid = listOf("an", "d", "ro", "id") println(listDroid.sumBy { it.length }) // 7 247
248. val mutableList = mutableListOf("an", "d", "ro", "id") mutableList.add("academy") It’s good style to use listOf, but mutableListOf is there when you need it. 248
249. val mutableList = mutableListOf("an", "d", "ro", "id") mutableList.add("academy") //[an, d, ro, id, academy] 249
250. val mutableList = mutableListOf("an", "d", "ro", "id") mutableList.add("academy") //[an, d, ro, id, academy] 250
251. “Take a given list and reverse it” 251
252. val droidList = listOf("an", "d", "ro", "id") val result = mutableListOf<String>() for (i in droidList.size - 1 downTo 0) { result.add(droidList[i]) } println(result) //[id, ro, d, an] 252
253. val droidList = listOf("an", "d", "ro", "id") val result = mutableListOf<String>() for (i in droidList.size - 1 downTo 0) { result.add(droidList[i]) } println(result) //[id, ro, d, an] 253
254. val droidList = listOf("an", "d", "ro", "id") val result = mutableListOf<String>() for (i in droidList.size - 1 downTo 0) { result.add(droidList[i]) } println(result) //[id, ro, d, an] 254
255. val droidList = listOf("an", "d", "ro", "id") val result = mutableListOf<String>() for (i in droidList.size - 1 downTo 0) { result.add(droidList[i]) } println(result) //[id, ro, d, an] 255
256. val droidList = listOf("an", "d", "ro", "id") val result = mutableListOf<String>() for (i in droidList.size - 1 downTo 0) { result.add(droidList[i]) } println(result) //[id, ro, d, an] 256
257. val droidList = listOf("an", "d", "ro", "id") val result = mutableListOf<String>() for (i in droidList.size - 1 downTo 0) { result.add(droidList[i]) } println(result) //[id, ro, d, an] 257
258. val droidList = listOf("an", "d", "ro", "id") val result = mutableListOf<String>() for (i in droidList.size - 1 downTo 0) { result.add(droidList[i]) } println(result) //[id, ro, d, an] 258
259. val listDroid = listOf("an", "d", "ro", "id") println(listDroid.reversed()) //[id, ro, d, an] 259
260. val listDroid = listOf("an", "d", "ro", "id") println(listDroid.reversed()) //[id, ro, d, an] 260
261. val listDroid = listOf("an", "d", "ro", "id") println(listDroid.reversed()) //[id, ro, d, an] 261
262. val listDroid = listOf("an", "d", "ro", "id") println(listDroid.reversed()) //[id, ro, d, an] 262
265. val languagesMap = mapOf( ) 265
266. val languagesMap = mapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) 266
267. val languagesMap = mapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) 267
268. val languagesMap = mapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) 268
269. val languagesMap = mapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) languagesMap.get("USA") 269
270. val languagesMap = mapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) languagesMap.get("USA") languagesMap["USA"] 270
271. val languagesMap = mapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) languagesMap.get("USA") languagesMap["USA"] languagesMap.getOrDefault("USA", "Hebrew") 271
272. val languagesMap = mapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) languagesMap.get("USA") languagesMap["USA"] languagesMap.getOrDefault("USA", "Hebrew") languagesMap.getOrElse("USA") { "Greek" } 272
273. val languagesMap = mapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) languagesMap.get("USA") languagesMap["USA"] languagesMap.getOrDefault("USA", "Hebrew") languagesMap.getOrElse("USA") { "Greek" } 273
274. val languagesMap = mapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) 274
275. val languagesMap = mapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) 275
276. val languagesMap = mapOf( // -> ImmutableMap "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) 276
277. val languagesMap = mutableMapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) 277
278. val languagesMap = mutableMapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) languagesMap.put("China", "Mandarin") 278
279. val languagesMap = mutableMapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) languagesMap.put("China", "Mandarin") languagesMap["China"] = "Mandarin" 279
280. val languagesMap = mutableMapOf( "USA" to "English", "Spain" to "Spanish", "Politics" to "Bull*hit" ) languagesMap.put("China", "Mandarin") languagesMap["China"] = "Mandarin" languagesMap.remove("China") 280
281. WORKSHOP!!! 281
282. // Let’s create a basic book class,with a title,author and year. class Book(val title: String, val author: String, val year: Int) 282
283. // Create a method that returns both the title and the author as a Pair. class Book(val title: String, val author: String, val year: Int){ fun getTitleAndAuthor(): Pair<String,String>{ return Pair(title, author) } } 283
284. // Create a method that returns the title, author and year as a Triple. class Book(val title: String, val author: String, val year: Int){ fun getTitleAndAuthor(): Pair<String,String>{ return Pair(title, author) } fun getTitleAndAuthorAndYear(): Triple<String,String, Int>{ return Triple(title, author, year) } } 284
285. // Create a book instance. fun main() { val book = Book("Orlando", "Virginia Woolf", 1928) } 285
286. // Print out the information about the book in a sentence fun main() { val book = Book("Orlando", "Virginia Woolf", 1928) val (title, author, year) = book.getTitleAndAuthorAndYear() println("Here is your book $title written by $author in $year.") } 286
287. // Print out the information about the book in a sentence fun main() { val book = Book("Orlando", "Virginia Woolf", 1928) val (title, author, year) = book.getTitleAndAuthorAndYear() println("Here is your book $title written by $author in $year.") } 287
290. const val primeMinister = "Bibi" 290
291. const val primeMinister = "Bibi" 291
293. val 293
294. what’s the difference? 294
295. • const val - The value is always determined at compile time 295
296. • const val - The value is always determined at compile time • val - The value that is assigned can be determined during programing execution. 296
297. class IceCream(val flavor: String = "Vanilla", val cone: Boolean = true){ ... } 297
298. class IceCream(val flavor: String = "Vanilla", val cone: Boolean = true){ ... } 298
299. class IceCream(val flavor: String = "Vanilla", val cone: Boolean = true){ ... } 299
300. class IceCream(val flavor: String = "Vanilla", val cone: Boolean = true){ ... } const val DEFAULT_FLAVOR: String = "Vanilla" 300
301. class IceCream(val flavor: String = DEFAULT_FLAVOR, val cone: Boolean = true){ ... } const val DEFAULT_FLAVOR: String = "Vanilla" 301
302. const val 302
303. • Top level const val 303
304. • Top level const val one = 1 const val 304
305. • Top level • Inside an object const val 305
306. • Top level • Inside an object object Constants { const val two = 2 } const val 306
307. • Top level • Inside an object • Inside a class inside a companion object const val 307
308. • Top level • Inside an object • Inside a class inside a companion object class MyClass{ companion object{ const val myConst = 42 } } const val 308
310. • Companion objects - initialized from the static constructor of the containing class. • objects - initialized lazily on the first access to that object. 310
311. • Companion objects - initialized from the static constructor of the containing class. • objects - initialized lazily on the first access to that object. 311
312. class IceCream(val flavor: String = DEFAULT_FLAVOR, val cone: Boolean = true) { ... } const val DEFAULT_FLAVOR: String = "Vanilla" 312
313. class IceCream(val flavor: String = DEFAULT_FLAVOR, val cone: Boolean = true) { ... companion object { const val DEFAULT_FLAVOR: String = "Vanilla" } } 313
314. class IceCream(val flavor: String = DEFAULT_FLAVOR, val cone: Boolean = true) { ... companion object { const val DEFAULT_FLAVOR: String = "Vanilla" } } 314
315. class IceCream(val flavor: String = DEFAULT_FLAVOR, val cone: Boolean = true) { ... companion object { const val DEFAULT_FLAVOR: String = "Vanilla" } } object Flavors { const val VANILLA: String = "Vanilla" } 315
316. class IceCream(val flavor: String = DEFAULT_FLAVOR, val cone: Boolean = true) { ... companion object { const val DEFAULT_FLAVOR: String = "Vanilla" } } object Flavors { const val VANILLA: String = "Vanilla" } 316
317. class IceCream(val flavor: String = DEFAULT_FLAVOR, val cone: Boolean = true) { ... companion object { const val DEFAULT_FLAVOR: String = Flavors.VANILLA } } object Flavors { const val VANILLA: String = "Vanilla" } 317
319. fun isNotNullOrEmpty(list: List<Int>?): Boolean = list != null || list.size > 0 319
320. fun main(list: MutableList<Int>?) { if (isNotNullOrEmpty(list)) { /** do something */ } } 320
321. fun swap(list: MutableList<Int>, index1: Int, index2: Int) { } 321
322. fun swap(list: MutableList<Int>, index1: Int, index2: Int) { val tmp = list[index1] list[index1] = list[index2] list[index2] = tmp } 322
323. fun main(list: MutableList<Int>?) { swap(list, 1, 5) } 323
324. fun main(list: MutableList<Int>?) { swap(list, 1, 5) // Error: list might be null } 324
325. fun main(list: MutableList<Int>?) { if (isNotNullOrEmpty(list)) { swap(list, 1, 5) } } 325
326. fun main(list: MutableList<Int>?) { if (isNotNullOrEmpty(list)) { swap(list!!, 1, 5) } } 326
327. fun main(list: MutableList<Int>?) { } 327
328. fun main(list: MutableList<Int>?) { if (list.isNotNullOrEmpty()) { /** do something */ } } 328
329. fun main(list: MutableList<Int>?) { if (list.isNotNullOrEmpty()) { /** do something */ } list.swap(1, 5) } 329
330. fun main(list: MutableList<Int>?) { if (list.isNotNullOrEmpty()) { /** do something */ } list?.swap(1, 5) } 330
331. Kotlin provides the ability to extend a class with new functionality without having to inherit from the class or use a design patterns such as Decorator. Kotlin provides this ability using two methods. • Extension function • Extension property 331
332. fun swap(list: MutableList<Int>, index1: Int, index2: Int) { val tmp = list[index1] list[index1] = list[index2] list[index2] = tmp } 332
333. fun swap(list: MutableList<Int>, index1: Int, index2: Int) { val tmp = list[index1] list[index1] = list[index2] list[index2] = tmp } 333
334. fun swap(index1: Int, index2: Int) { val tmp = list[index1] list[index1] = list[index2] list[index2] = tmp } 334
335. fun MutableList<Int> swap(index1: Int, index2: Int) { val tmp = list[index1] list[index1] = list[index2] list[index2] = tmp } 335
336. fun MutableList<Int>.swap(index1: Int, index2: Int) { val tmp = list[index1] list[index1] = list[index2] list[index2] = tmp } 336
337. fun MutableList<Int>.swap(index1: Int, index2: Int) { val tmp = list[index1] list[index1] = list[index2] list[index2] = tmp } The class/type we want to extend 337
338. fun MutableList<Int>.swap(index1: Int, index2: Int) { val tmp = list[index1] list[index1] = list[index2] list[index2] = tmp } The function we add 338
339. fun MutableList<Int>.swap(index1: Int, index2: Int) { val tmp = list[index1] list[index1] = list[index2] list[index2] = tmp } 339
340. fun MutableList<Int>.swap(index1: Int, index2: Int) { val tmp = list[index1] list[index1] = list[index2] list[index2] = tmp } Compilation error: unknown variable "list" 340
341. fun MutableList<Int>.swap(index1: Int, index2: Int) { val tmp = list[index1] list[index1] = list[index2] list[index2] = tmp } 341
342. fun MutableList<Int>.swap(index1: Int, index2: Int) { val tmp = this[index1] this[index1] = this[index2] this[index2] = tmp } 342
343. fun MutableList<Int>.swap(index1: Int, index2: Int) { val tmp = this[index1] this[index1] = this[index2] this[index2] = tmp } 'this' corresponds to the list (receiver) 343
344. fun isNotNullOrEmpty(list: List<Int>?): Boolean = list != null || list.size > 0 344
345. fun isNotNullOrEmpty(): Boolean = list != null || list.size > 0 345
346. fun List<Int>?.isNotNullOrEmpty(): Boolean = list != null || list.size > 0 346
347. fun List<Int>?.isNotNullOrEmpty(): Boolean = list != null || list.size > 0 Nullable receiver 347
348. fun List<Int>?.isNotNullOrEmpty(): Boolean = list != null || list.size > 0 348
349. fun List<Int>?.isNotNullOrEmpty(): Boolean = list != null || list.size > 0 349
350. fun List<Int>?.isNotNullOrEmpty(): Boolean = this != null || list.size > 0 350
351. fun List<Int>?.isNotNullOrEmpty(): Boolean = this != null || list.size > 0 351
352. fun List<Int>?.isNotNullOrEmpty(): Boolean = this != null || this.size > 0 352
353. fun List<Int>?.isNotNullOrEmpty(): Boolean = this != null || this.size > 0 Wrong 353
354. fun List<Int>?.isNotNullOrEmpty(): Boolean = this != null || this.size > 0 Wrong. kinda... 354
355. fun List<Int>?.isNotNullOrEmpty(): Boolean = this != null || this.size > 0 355
356. fun List<Int>?.isNotNullOrEmpty(): Boolean = this != null || size > 0 this = receiver$List<Int> 356
357. class ExtendedList : MutableList<Int> { fun isNotNullOrEmpty() { this != null || this.size > 0 } } 357
358. public static boolean isNotNullOrEmpty(@Nullable List $receiver) { return $receiver != null && $receiver.size() > 0; } 358
360. class IceCream(...) { var topping: Topping } fun main(iceCream: IceCream) { iceCream.topping = Toppings.Chocolate } 360
361. fun IceCream.withChocolate() { topping = Toppings.Chocolate } 361
362. fun IceCream.withChocolate() { topping = Toppings.Chocolate } fun main(iceCream: IceCream) { iceCream.withChocolate() } 362
363. fun IceCream.withChocolate() { topping = Toppings.Chocolate } 363
364. fun IceCream.withChocolate(): IceCream { topping = Toppings.Chocolate return this } 364
365. fun main(iceCream: IceCream) { val sunday = SundayIceCream(iceCream.withChocolate()) } 365
366. fun main(iceCream: IceCream) { val sunday = SundayIceCream(iceCream.withChocolate()) sunday.addOreos() } 366
367. fun IceCream.withChocolate(): IceCream { topping = Toppings.Chocolate return this } 367
368. fun IceCream.withChocolate(): IceCream { topping = Toppings.Chocolate return this } fun IceCream.asSunday(): SundayIceCream = SundayIceCream(this) 368
369. fun main(iceCream: IceCream) { iceCream } 369
370. fun main(iceCream: IceCream) { iceCream.asSunday() } 370
371. fun main(iceCream: IceCream) { iceCream.asSunday().withChocolate() } 371
372. fun main(iceCream: IceCream) { iceCream.asSunday().withChocolate().addOreos() } 372
373. class IceCreamShop { fun main(iceCream: IceCream) { iceCream.asSunday().withChocolate().addOreos() } fun IceCream.withChocolate(): IceCream { /** code */ } fun IceCream.asSunday(): SundayIceCream = /** code */ } 373
374. class IceCreamShop { fun main(iceCream: IceCream) { iceCream.asSunday().withChocolate().addOreos() } fun IceCream.withChocolate(): IceCream { /** code */ } fun IceCream.asSunday(): SundayIceCream = /** code */ } 374
375. class IceCreamShop { fun main(iceCream: IceCream) { iceCream.asSunday().withChocolate().addOreos() } fun IceCream.withChocolate(): IceCream { /** code */ } fun IceCream.asSunday(): SundayIceCream = /** code */ } 375
376. class House { fun main(iceCream: IceCream) { } } 376
377. class House { fun main(iceCream: IceCream) { iceCream.asSunday().withChocolate().addOreos() } } 377
378. class House { fun main(iceCream: IceCream) { iceCream.asSunday().withChocolate().addOreos() } } Compilation error: "asSunday" is not a function in IceCream class 378
379. class House { fun main(iceCream: IceCream) { val shop = IceCreamShop() shop.asSunday().withChocolate().addOreos() } } Compilation error: "asSunday" is not a function in IceCreamShop class 379
381. package com.android.academy 381
382. package com.android.academy fun IceCream.withChocolate(): IceCream { /** code */ } fun IceCream.asSunday(): SundayIceCream = /** code */ 382
383. import com.android.academy.IceCreamExtensions.asSunday import com.android.academy.IceCreamExtensions.withChocolate class House { fun main(iceCream: IceCream) { iceCream.asSunday().withChocolate().addOreos() } } 383
385. fun <F, S> F.to(second: S): Pair<F, S> Pair(this, second) 385
386. fun main() { val iceCream = IceCream() val topping = Toppings.Chocolate iceCream.to(topping) // -> Pair(iceCream, Chocolate) } 386
387. fun main() { val iceCream = IceCream() val topping = Toppings.Chocolate iceCream to topping // -> Pair(iceCream, Chocolate) } 387
388. fun <F, S> F.to(second: S): Pair<F, S> Pair(this, second) 388
389. fun <F, S> F.to(second: S): Pair<F, S> Pair(this, second) One receiver 389
390. fun <F, S> F.to(second: S): Pair<F, S> Pair(this, second) One parameter 390
391. fun <F, S> F.to(second: S): Pair<F, S> Pair(this, second) 391
392. infix fun <F, S> F.to(second: S): Pair<F, S> Pair(this, second) 392
393. fun main() { val iceCream = IceCream() val topping = Toppings.Chocolate iceCream to topping // -> Pair(iceCream, Chocolate) } 393
395. val <E> List<E>.last: E get() = this[size] 395
396. fun main() { val names = listOf("Gil", "Eden", "Hadas") println(names.last) // -> "Hadas" } 396
397. val <E> List<E>.last: E get() = this[size] 397
398. var <E> MutableList<E>.last: E get() = this[size] val <E> List<E>.last: E get() = this[size] 398
399. var <E> MutableList<E>.last: E get() = this[size] set(value) { this[size] = value } val <E> List<E>.last: E get() = this[size] 399
400. fun main() { val names = listOf("Gil", "Eden", "Hadas") println(names.last) // -> "Hadas" } 400
401. fun main() { val names = mutableListOf("Gil", "Eden", "Hadas") println(names.last) // -> "Hadas" } 401
402. fun main() { val names = mutableListOf("Gil", "Eden", "Hadas") println(names.last) // -> "Hadas" names.last = "Yonatan" } 402
403. fun main() { val names = mutableListOf("Gil", "Eden", "Hadas") println(names.last) // -> "Hadas" names.last = "Yonatan" println(names) // -> ["Gil", "Eden", "Yonatan"] } 403
404. public static Object getLast(@NotNull List $last) { Intrinsics.checkParameterIsNotNull($last, "$last"); return $last.get($last.size()); } 404
405. public static Object getLast(@NotNull List $last) { Intrinsics.checkParameterIsNotNull($last, "$last"); return $last.get($last.size()); } 405
406. public void checkParameterIsNotNull(Object value, String param) { if (value == null) { throwParameterIsNullException(param); } } 406
407. public static Object getLast(@NotNull List $last) { Intrinsics.checkParameterIsNotNull($last, "$last"); return $last.get($last.size()); } 407
408. public static Object getLast(@NotNull List $last) { Intrinsics.checkParameterIsNotNull($last, "$last"); return $last.get($last.size()); } public static void setLast(@NotNull List $last, Object value) { Intrinsics.checkParameterIsNotNull($last, "$last"); $last.set($last.size(), value); } 408
410. class Speaker() { fun speak(content: String) { println(content) } } 410
411. fun Speaker.meow() { speak("meow") } 411
412. fun main() { val speaker = Speaker() speaker.meow() } 412
413. WORKSHOP!!! 413