Slide 2
Slide 2 text
This is not…
Slide 3
Slide 3 text
How great code reviews are, and what’s
the best way to do them
This is not…
Slide 4
Slide 4 text
and how to get your
management onboard with the idea
Why you should use Kotlin for Android
development…
How great code reviews are, and what’s
the best way to do them
This is not…
Slide 5
Slide 5 text
and how to get your
management onboard with the idea
Why you should use Kotlin for Android
development…
All the awesome things that are in the
Kotlin standard library
How great code reviews are, and what’s
the best way to do them
This is not…
Slide 6
Slide 6 text
Life is Great and Everything Will Be Ok,
Kotlin is Here
Christina Lee, Jake Wharton
Google I/O '17
Dissecting the stdlib
Huyen Tue Dao
KotlinConf 2018
Code Review Best Practices
Trisha Gee
SCLConf 2018
This is not…
Slide 7
Slide 7 text
No content
Slide 8
Slide 8 text
No content
Slide 9
Slide 9 text
No content
Slide 10
Slide 10 text
No content
Slide 11
Slide 11 text
No content
Slide 12
Slide 12 text
No content
Slide 13
Slide 13 text
99000 lines of Kotlin code
5700 commits
700 merge requests
Slide 14
Slide 14 text
No content
Slide 15
Slide 15 text
No content
Slide 16
Slide 16 text
No content
Slide 17
Slide 17 text
No content
Slide 18
Slide 18 text
No content
Slide 19
Slide 19 text
No content
Slide 20
Slide 20 text
No content
Slide 21
Slide 21 text
No content
Slide 22
Slide 22 text
Breaking the habit
Slide 23
Slide 23 text
Breaking the habit
Enums
Slide 24
Slide 24 text
Breaking the habit
Enums Lambdas
Slide 25
Slide 25 text
Breaking the habit
Enums Lambdas Typechecks
Slide 26
Slide 26 text
Breaking the habit
Enums Lambdas Typechecks
is
as
as?
Slide 27
Slide 27 text
entries: ArrayList) {
fun updateColors(chart: ,
}
PieChart
Slide 28
Slide 28 text
entries: ArrayList) {
fun updateColors(chart: ,
val colors = ArrayList()
}
PieChart
Slide 29
Slide 29 text
entries: ArrayList) {
fun updateColors(chart: ,
val colors = ArrayList()
entries.forEach { entry ->
colors.add(entry.data as Int)
}
}
PieChart
Slide 30
Slide 30 text
entries: ArrayList) {
fun updateColors(chart: ,
val colors = ArrayList()
entries.forEach { entry ->
colors.add(entry.data as Int)
}
chart.colors = colors
}
PieChart
Slide 31
Slide 31 text
entries: ArrayList) {
fun updateColors(chart: ,
val colors = ArrayList()
entries.forEach { entry ->
colors.add(entry.data as Int)
}
chart.colors = colors
}
PieChart
Slide 32
Slide 32 text
fun PieChart.updateColors(entries:
val colors = ArrayList()
entries.forEach { entry ->
colors.add(entry.data as Int)
}
this.colors = colors
}
List) {
Array
Slide 33
Slide 33 text
fun PieChart.updateColors(entries:
val colors = ArrayList()
entries.forEach { entry ->
colors.add(entry.data as Int)
}
this.colors = colors
}
List) {
Slide 34
Slide 34 text
fun PieChart.updateColors(entries:
val colors = ArrayList()
entries.forEach { entry ->
colors.add(entry.data as Int)
}
this.colors = colors
}
List) {
Slide 35
Slide 35 text
fun PieChart.updateColors(entries: List) {
val colors = mutableListOf()
entries.forEach { entry ->
colors.add(entry.data as Int)
}
this.colors = colors
}
Slide 36
Slide 36 text
fun PieChart.updateColors(entries: List) {
val colors = mutableListOf()
entries.forEach { entry ->
colors.add(entry.data as Int)
}
this.colors = colors
}
Slide 37
Slide 37 text
fun PieChart.updateColors(entries: List) {
val colors = mutableListOf()
entries.map { entry ->
colors.add( )
}
this.colors = colors
}
entry.data as Int
Slide 38
Slide 38 text
fun PieChart.updateColors(entries: List) {
val colors = mutableListOf()
entries.map { entry ->
}
this.colors = colors
}
entry.data as Int
Slide 39
Slide 39 text
fun PieChart.updateColors(entries: List) {
this.colors = colors
}
entry.data as Int
}
entries.map { entry ->
val colors =
Slide 40
Slide 40 text
fun PieChart.updateColors(entries: List) {
this.colors = colors
}
entry.data as Int
}
entries.map { entry ->
val colors =
Slide 41
Slide 41 text
fun PieChart.updateColors(entries: List) {
this.colors
entry.data as Int
}
}
= entries.map { entry ->
Slide 42
Slide 42 text
No content
Slide 43
Slide 43 text
No content
Slide 44
Slide 44 text
fun getExaminationResult(resultId: UUID): ExaminationResult {
}
Slide 45
Slide 45 text
fun getExaminationResult(resultId: UUID): ExaminationResult {
return getItemGroups()
}
Slide 46
Slide 46 text
fun getExaminationResult(resultId: UUID): ExaminationResult {
return getItemGroups()
}
.map { it.toExaminationResult() }
Slide 47
Slide 47 text
fun getExaminationResult(resultId: UUID): ExaminationResult {
return getItemGroups()
}
.map { it.toExaminationResult() }
.first { it.id == resultId }
Slide 48
Slide 48 text
fun getExaminationResult(resultId: UUID): ExaminationResult {
return getItemGroups()
}
.map { it.toExaminationResult() }
.first { it.id == resultId }
Slide 49
Slide 49 text
fun getExaminationResult(resultId: UUID): ExaminationResult {
return getItemGroups()
}
.map { it.toExaminationResult() }
.first { it.id == resultId }
Slide 50
Slide 50 text
fun getExaminationResult(resultId: UUID): ExaminationResult {
return getItemGroups()
}
.first { it.id == resultId }
.map { it }
.toExaminationResult()
Slide 51
Slide 51 text
fun getExaminationResult(resultId: UUID): ExaminationResult {
return getItemGroups()
}
.first { it.id == resultId }
.toExaminationResult()
Slide 52
Slide 52 text
val events: List = getAllEvents()
val upcoming = events.filter {
it.date >
}
OffsetDateTime.now()
Slide 53
Slide 53 text
val events: List = getAllEvents()
val upcoming = events.filter {
it.date >
}
OffsetDateTime.now()
val now =
now
Slide 54
Slide 54 text
fun startBluetoothLeScan() {
}
Slide 55
Slide 55 text
fun startBluetoothLeScan() {
val scanner = BluetoothAdapter.getDefaultAdapter()
.bluetoothLeScanner
}
Slide 56
Slide 56 text
fun startBluetoothLeScan() {
val scanner = BluetoothAdapter.getDefaultAdapter()
.bluetoothLeScanner
/* ... */
}
Slide 57
Slide 57 text
fun startBluetoothLeScan() {
val scanner = BluetoothAdapter.getDefaultAdapter()
.bluetoothLeScanner
/* ... */
scanner
}
.startScan(/* ... */)
Slide 58
Slide 58 text
fun startBluetoothLeScan() {
val scanner = BluetoothAdapter.getDefaultAdapter()
.bluetoothLeScanner
/* ... */
scanner?
}
.startScan(/* ... */)
Slide 59
Slide 59 text
if (scanner != null) {
} else {
/* ¯\_(ツ)_/¯ */
}
}
fun startBluetoothLeScan() {
val scanner = BluetoothAdapter.getDefaultAdapter()
.bluetoothLeScanner
/* ... */
scanner.startScan(/* ... */)
Slide 60
Slide 60 text
No content
Slide 61
Slide 61 text
No content
Slide 62
Slide 62 text
data class DailyFluidConsumption(
)
Slide 63
Slide 63 text
data class DailyFluidConsumption(
val quantity: Double,
)
Slide 64
Slide 64 text
data class DailyFluidConsumption(
val quantity: Double,
val recommended: Double = 4.0,
)
Slide 65
Slide 65 text
data class DailyFluidConsumption(
val quantity: Double,
val recommended: Double = 4.0,
val percentage: Int =
((quantity / recommended) * 100)
.roundToInt()
.coerceIn(0..100)
)
Slide 66
Slide 66 text
data class DailyFluidConsumption(
val quantity: Double,
val recommended: Double = 4.0
)
val percentage: Int =
((quantity / recommended) * 100)
.roundToInt()
.coerceIn(0..100)
Slide 67
Slide 67 text
data class DailyFluidConsumption(
val quantity: Double,
val recommended: Double = 4.0
)
val DailyFluidConsumption.percentage: Int
((quantity / recommended) * 100)
.roundToInt()
.coerceIn(0..100)
Slide 68
Slide 68 text
data class DailyFluidConsumption(
val quantity: Double,
val recommended: Double = 4.0
)
val DailyFluidConsumption.percentage: Int
get() = ((quantity / recommended) * 100)
.roundToInt()
.coerceIn(0..100)
Slide 69
Slide 69 text
zsmb.co/data-classes-arent-that-magical
Slide 70
Slide 70 text
class Ingredient(
val id: UUID = UUID.randomUUID(),
val name: String = "",
val quantity: Double? = null,
val unit: String? = null,
val imageId: UUID? = null
)
Slide 71
Slide 71 text
class Ingredient(
val id: UUID = UUID.randomUUID(),
val name: String = "",
val quantity: Double? = null,
val unit: String? = null,
val imageId: UUID? = null
)
Slide 72
Slide 72 text
class Ingredient(
val id: UUID = UUID.randomUUID(),
val name: String = "",
val quantity: Double? = null,
val unit: String? = null,
val imageId: UUID? = null
)
Slide 73
Slide 73 text
class Ingredient(
val id: UUID = UUID.randomUUID(),
val name: String = "",
val quantity: Double? = null,
val unit: String? = null,
val imageId: UUID? = null
)
Ingredient(id, "Pixie dust", 6.28, "teaspoon")
Slide 74
Slide 74 text
class Ingredient(
val id: UUID = UUID.randomUUID(),
val name: String = "",
val quantity: Double? = null,
val unit: String? = null,
val imageId: UUID? = null
)
Ingredient(id, "Pixie dust", 6.28, "teaspoon")
Slide 75
Slide 75 text
class Ingredient(
val id: UUID = UUID.randomUUID(),
val name: String = "",
val quantity: Double? = null,
val unit: String? = null,
val imageId: UUID? = null
)
Ingredient(id, "Pixie dust", 6.28, "teaspoon")
Slide 76
Slide 76 text
class Ingredient(
val id: UUID,
val name: String,
val quantity: Double?,
val unit: String?,
val imageId: UUID?
)
Ingredient(id, "Pixie dust", 6.28, "teaspoon")
Slide 77
Slide 77 text
class Ingredient(
val id: UUID,
val name: String,
val quantity: Double?,
val unit: String?,
val imageId: UUID?
)
Ingredient(id, "Pixie dust", 6.28, "teaspoon", null)
Slide 78
Slide 78 text
id =
name =
quantity =
unit =
imageId =
id,
6.28,
)
"teaspoon",
null
Ingredient(
"Pixie dust",
class Ingredient(
val id: UUID,
val name: String,
val quantity: Double?,
val unit: String?,
val imageId: UUID?
)
Slide 79
Slide 79 text
suspend fun
Slide 80
Slide 80 text
suspend fun getValidMeasurements(
measurements: List
): List {
}
Slide 81
Slide 81 text
suspend fun getValidMeasurements(
measurements: List
): List {
return measurements.filter {
}
}
Slide 82
Slide 82 text
suspend fun getValidMeasurements(
measurements: List
): List {
return measurements.filter {
val validator = getValidatorForType(it.type)
}
}
Slide 83
Slide 83 text
suspend fun getValidMeasurements(
measurements: List
): List {
return measurements.filter {
val validator = getValidatorForType(it.type)
it.value in (validator.minValue..validator.maxValue)
}
}
Slide 84
Slide 84 text
suspend fun getValidMeasurements(
measurements: List
): List {
return measurements.filter { measurement ->
val validator = getValidatorForType(measurement.type)
measurement.value in (validator.minValue..validator.maxValue)
}
}
Slide 85
Slide 85 text
return measurements.filter { measurement ->
val validator = getValidatorForType(measurement.type)
measurement.value in (validator.minValue..validator.maxValue)
}
}
suspend fun getValidMeasurements(
measurements: List
): List {
Slide 86
Slide 86 text
return measurements.filter { measurement ->
val validator = getValidatorForType(measurement.type)
measurement.value in (validator.minValue..validator.maxValue)
}
}
suspend fun getValidMeasurements(
measurements: List
): List {
Slide 87
Slide 87 text
return measurements.filter { measurement ->
val validator = getValidatorForType(measurement.type)
measurement.value in (validator.minValue..validator.maxValue)
}
}
suspend fun getValidMeasurements(
measurements: List
): List {
Slide 88
Slide 88 text
val validatorsByType = getAllValidators()
suspend fun getValidMeasurements(
measurements: List
): List {
}
return measurements.filter { measurement ->
val validator = getValidatorForType(measurement.type)
measurement.value in (validator.minValue..validator.maxValue)
}
Slide 89
Slide 89 text
val validatorsByType = getAllValidators().associateBy { it.type }
suspend fun getValidMeasurements(
measurements: List
): List {
}
return measurements.filter { measurement ->
val validator = getValidatorForType(measurement.type)
measurement.value in (validator.minValue..validator.maxValue)
}
Slide 90
Slide 90 text
val validatorsByType = getAllValidators()
suspend fun getValidMeasurements(
measurements: List
): List {
}
return measurements.filter { measurement ->
val validator = validatorsByType.getValue(measurement.type)
measurement.value in (validator.minValue..validator.maxValue)
}
.associateBy { it.type }
Slide 91
Slide 91 text
No content
Slide 92
Slide 92 text
No content
Slide 93
Slide 93 text
No content
Slide 94
Slide 94 text
No content
Slide 95
Slide 95 text
No content
Slide 96
Slide 96 text
No content
Slide 97
Slide 97 text
No content
Slide 98
Slide 98 text
No content
Slide 99
Slide 99 text
No content
Slide 100
Slide 100 text
No content
Slide 101
Slide 101 text
No content
Slide 102
Slide 102 text
No content
Slide 103
Slide 103 text
No content
Slide 104
Slide 104 text
No content
Slide 105
Slide 105 text
No content
Slide 106
Slide 106 text
No content
Slide 107
Slide 107 text
fun add (x:Int,y: Int) :Int{
return x +y
}
fun main() {
println( add(2,3) )
}
Slide 108
Slide 108 text
fun add(x: Int, y: Int): Int {
return x + y
}
fun main() {
println(add(2, 3))
}
Slide 109
Slide 109 text
What did you miss about Java?
Slide 110
Slide 110 text
Related talks
• Code Review Best Practices
Trisha Gee, SCLConf 2018
https://www.youtube.com/watch?v=jXi8h44cbQA
• Life is Great and Everything Will Be Ok, Kotlin is Here
Christina Lee & Jake Wharton, Google I/O ‘17
https://www.youtube.com/watch?v=fPzxfeDJDzY
• Dissecting the stdlib
Huyen Tue Dao, KotlinConf 2018
https://www.youtube.com/watch?v=Fzt_9I733Yg
Slide 111
Slide 111 text
Learning resources
• Kotlin in Action, Dmitry Jemerov and Svetlana Isakova
https://www.manning.com/books/kotlin-in-action
• Coursera course, Andrey Breslav and Svetlana Isakova
https://www.coursera.org/learn/kotlin-for-java-developers
• O’Reilly courses, Hadi Hariri
https://hadihariri.com/2016/11/01/oreilly-kotlin-course/
Slide 112
Slide 112 text
Learning resources
• Kotlin Bootcamp for Programmers
https://eu.udacity.com/course/kotlin-bootcamp-for-
programmers--ud9011
• Developing Android Apps with Kotlin
https://eu.udacity.com/course/developing-android-apps-with-
kotlin--ud9012
Slide 113
Slide 113 text
Further reading
• Data classes aren’t (that) magical
https://zsmb.co/data-classes-arent-that-magical/
Slide 114
Slide 114 text
zsmb13
zsmb.co/talks