Kotlin: from No to Yes

Transcript

1. From NO to…Yes!
2. Cristian Monforte @cmonfortep Android dev at…
3. Cristian Monforte @cmonfortep Android dev at…
4. Consider kotlin Start using kotlin Convince your company
5. • This is not Kotlin vs Java vs Scala • This is not a ‘how to use kotlin' talk
6. • My opinions • Other dev opinions • Company opinions
7. • My opinions • Other dev opinions • Company opinions
8. Our first steps…
9. Our first steps… we started with unit tests
10. Our first steps… we started with unit tests Some of us fell in love with Kotlin
11. Our first steps… we started with unit tests Some of us fell in love with Kotlin Kaizen Circle
12. Our first steps… we started with unit tests Some of us fell in love with Kotlin Kaizen Circle I voted NO
13. Our first steps… we started with unit tests Some of us fell in love with Kotlin Kaizen Circle I voted NO …but the team voted Yes
14. • antonio leiva droidcon photo • material fest photo
15. • Scala was my personal bet • Nulls… • Learning while writing code in production • JetBrains support • how does kotlin coexist with android? • I don’t need kotlin…it’s only syntactic sugar • why only Android?
16. http://langpop.corger.nl/
17. Junior again…
18. • Hiring • Clients • Complex apps • Not an official language • Size of teams Concerns
19. • Shared knowledge • Solving problems together • More resources for mentoring • PR reviewed by more people Good for big teams
20. After 2 days…we received an email…
21. After 2 days…we received an email… …Asking us to STOP producing code in Kotlin
22. After 2 days…we received an email… …Asking us to STOP producing code in Kotlin
23. After 2 days…we received an email… …Asking us to STOP producing code in Kotlin The company has to decide too
25. • 15% crashes are NPE • Be faster, Be concise, Be clean • Kotlin-Swift • New possibilities • Kotlin documentation and trainings • Remove third-party libs Pros
26. • Tooling • StackOverflow driven development • Java-Kotlin projects • Onboarding for freelancers Cons
27. • Tests / project libraries / module • Define conventions and tools • Refactor classes backed by tests • Everything new in kotlin Roll-out plan
28. and talks about kotlin in many conferences, opensource projects / libraries, …
29. Learning while writing code in production
30. Learning while writing code in production
31. https://github.com/rocboronat/bacon-free-days-kotlin
32. • Kotlin vs RxJava • Plugin • No need to change paradigm
33. Nullability as a Type var nullableString: String? = "hello world"
 var length: Int = nullableString.length //compile error
 length = nullableString?.length //compile error
 length = nullableString?.length ?: 0
34. Nullability as a Type var nullableString: String? = "hello world"
 var length: Int = nullableString.length //compile error
 length = nullableString?.length //compile error
 length = nullableString?.length ?: 0 if (nullableString != null) {
 length = nullableString.length
 length = nullableString?.length
 } length = nullableString!!.length
 length = nullableString.length
35. Nullability as a Type var nullableString: String? = "hello world"
 var length: Int = nullableString.length //compile error
 length = nullableString?.length //compile error
 length = nullableString?.length ?: 0 if (nullableString != null) {
 length = nullableString.length
 length = nullableString?.length
 } length = nullableString!!.length
 length = nullableString.length var notNullString: String
 notNullString = null //compile error
 notNullString = StringGenerator.itsATrap() //boom!
36. • concise, less verbose, string interpolation, smart cast, sealed classes, streams, lambdas, immutability first, kotlin size, static nullability checks, reduce common errors…
37. let, apply, with, run fun printUserLet(user: User?): String {
 return user?.let { //(T) -> R
 it.formattedName()
 } ?: ""
 }
38. let, apply, with, run fun printUserLet(user: User?): String {
 return user?.let { //(T) -> R
 it.formattedName()
 } ?: ""
 } fun printUserApply(user: User?): String {
 return user?.apply {//T.() -> Unit
 formattedName()
 }?.formattedName() ?: ""
 }
39. let, apply, with, run fun printUserLet(user: User?): String {
 return user?.let { //(T) -> R
 it.formattedName()
 } ?: ""
 } fun printUserApply(user: User?): String {
 return user?.apply {//T.() -> Unit
 formattedName()
 }?.formattedName() ?: ""
 } fun printUserWith(user: User?): String {
 return with(user) {//T.() -> R
 this?.formattedName()
 } ?: ""
 }
40. let, apply, with, run fun printUserLet(user: User?): String {
 return user?.let { //(T) -> R
 it.formattedName()
 } ?: ""
 } fun printUserApply(user: User?): String {
 return user?.apply {//T.() -> Unit
 formattedName()
 }?.formattedName() ?: ""
 } fun printUserWith(user: User?): String {
 return with(user) {//T.() -> R
 this?.formattedName()
 } ?: ""
 } fun printUserRun(user: User?): String {
 return user?.run {//T.() -> R
 formattedName()
 } ?: ""
 }
41. JvmOverloads, named and default params @JvmOverloads fun dummyMethod(dummyString: String? = "", dummyBoolean: Boolean = true) {
 }
 
 fun dummyMethod(dummyLong: Long?, dummyBoolean: Boolean) {
 }
42. JvmOverloads, named and default params @JvmOverloads fun dummyMethod(dummyString: String? = "", dummyBoolean: Boolean = true) {
 }
 
 fun dummyMethod(dummyLong: Long?, dummyBoolean: Boolean) {
 } public static void dummyCall() {
 DefaultParams.dummyMethod(null, true); //Ambiguous method call
 } fun sample() {
 dummyMethod(null, true) //Overload resolution ambiguity
 }
43. JvmOverloads, named and default params @JvmOverloads fun dummyMethod(dummyString: String? = "", dummyBoolean: Boolean = true) {
 }
 
 fun dummyMethod(dummyLong: Long?, dummyBoolean: Boolean) {
 } fun sample() {
 dummyMethod(dummyString = null, dummyBoolean = true)
 } public static void dummyCall() {
 DefaultParams.dummyMethod(null, true); //Ambiguous method call
 } fun sample() {
 dummyMethod(null, true) //Overload resolution ambiguity
 }
44. Extensions const val NO_FLAGS: Int = 0
 
 fun Activity.showKeyboard(flags: Int = NO_FLAGS) =
 (getSystemService(Context.INPUT_METHOD_SERVICE) as? InputMethodManager)?.apply {
 toggleSoftInput(InputMethodManager.SHOW_FORCED, flags)
 }
45. Extensions const val NO_FLAGS: Int = 0
 
 fun Activity.showKeyboard(flags: Int = NO_FLAGS) =
 (getSystemService(Context.INPUT_METHOD_SERVICE) as? InputMethodManager)?.apply {
 toggleSoftInput(InputMethodManager.SHOW_FORCED, flags)
 } class keyboardActivity : AppCompatActivity() {
 override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState)
 showKeyboard()
 }
 }
46. High order methods fun SharedPreferences.edit(func: SharedPreferences.Editor.() -> Unit) {
 val editor = edit()
 editor.func()
 editor.apply()
 }

47. High order methods fun Activity.getSharedPref(name: String = "DefaultSP",
 mode: Int = Context.MODE_PRIVATE): SharedPreferences {
 return getSharedPreferences(name, mode)
 } fun SharedPreferences.edit(func: SharedPreferences.Editor.() -> Unit) {
 val editor = edit()
 editor.func()
 editor.apply()
 }

48. High order methods fun Activity.getSharedPref(name: String = "DefaultSP",
 mode: Int = Context.MODE_PRIVATE): SharedPreferences {
 return getSharedPreferences(name, mode)
 } fun SharedPreferences.edit(func: SharedPreferences.Editor.() -> Unit) {
 val editor = edit()
 editor.func()
 editor.apply()
 }
 class SharedPrefActivity : AppCompatActivity() {
 override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState)
 
 getSharedPref().edit {
 putString("Location", "Madrid")
 putInt("Year", 2017)
 putBoolean("Visited", true)
 }
 }
 }
49. Sealed class sealed class CustomException {
 object UnkownException : CustomException()
 class ParseException(val description: String) : CustomException()
 class NetworkException(val code: Int, val description: String) : CustomException()
 }
 
 fun manageExceptions(exception: CustomException) = when (exception) {
 CustomException.UnkownException -> println("no idea")
 is CustomException.ParseException -> println(exception.description)
 is CustomException.NetworkException -> println("${exception.code}: ${exception.description}")
 }
50. Delegation interface InterfaceA {
 fun methodA()
 }
 
 interface InterfaceB {
 fun methodB()
 }
 
 class ImplA(val x: Int) : InterfaceA {
 override fun methodA() {
 print(x)
 }
 }
 
 class ImplB(val x: Int) : InterfaceB {
 override fun methodB() {
 print(x)
 }
 }
51. Delegation interface InterfaceA {
 fun methodA()
 }
 
 interface InterfaceB {
 fun methodB()
 }
 
 class ImplA(val x: Int) : InterfaceA {
 override fun methodA() {
 print(x)
 }
 }
 
 class ImplB(val x: Int) : InterfaceB {
 override fun methodB() {
 print(x)
 }
 } class AandB(a: InterfaceA, b: InterfaceB) : InterfaceA by a, InterfaceB by b
52. Software Patterns object SingleInstance {
 var dummyBool: Boolean = true } https://github.com/dbacinski/Design-Patterns-In-Kotlin
53. Software Patterns object SingleInstance {
 var dummyBool: Boolean = true } public class XingUser {
 private final int id;
 private final String name;
 private final String email;
 
 public static class Builder {
 private final int id;
 private final String name;
 private String email = "";
 
 public Builder(int id, String name) {
 this.id = id;
 this.name = name;
 }
 
 public Builder email(String email) {
 this.email = email;
 return this;
 }
 
 public XingUser build() {
 return new XingUser(this);
 }
 }
 
 private XingUser(Builder builder) {
 id = builder.id;
 name = builder.name;
 email = builder.email;
 }
 } https://github.com/dbacinski/Design-Patterns-In-Kotlin
54. Software Patterns object SingleInstance {
 var dummyBool: Boolean = true } public class XingUser {
 private final int id;
 private final String name;
 private final String email;
 
 public static class Builder {
 private final int id;
 private final String name;
 private String email = "";
 
 public Builder(int id, String name) {
 this.id = id;
 this.name = name;
 }
 
 public Builder email(String email) {
 this.email = email;
 return this;
 }
 
 public XingUser build() {
 return new XingUser(this);
 }
 }
 
 private XingUser(Builder builder) {
 id = builder.id;
 name = builder.name;
 email = builder.email;
 }
 } class XingUser(val id: Int,
 val name: String,
 val email: String = "",
 val premium: Boolean = false) https://github.com/dbacinski/Design-Patterns-In-Kotlin
55. Software Patterns object SingleInstance {
 var dummyBool: Boolean = true } public class XingUser {
 private final int id;
 private final String name;
 private final String email;
 
 public static class Builder {
 private final int id;
 private final String name;
 private String email = "";
 
 public Builder(int id, String name) {
 this.id = id;
 this.name = name;
 }
 
 public Builder email(String email) {
 this.email = email;
 return this;
 }
 
 public XingUser build() {
 return new XingUser(this);
 }
 }
 
 private XingUser(Builder builder) {
 id = builder.id;
 name = builder.name;
 email = builder.email;
 }
 } class XingUser(val id: Int,
 val name: String,
 val email: String = "",
 val premium: Boolean = false) XingUser(id = 1,
 name = "Cristian")
 
 XingUser(id = 1,
 name = "Cristian",
 email = "cristian@mailinator.com")
 
 XingUser(id = 1,
 name = "Cristian",
 premium = true) https://github.com/dbacinski/Design-Patterns-In-Kotlin
56. Software Patterns https://github.com/dbacinski/Design-Patterns-In-Kotlin class Printer(val stringStrategy: (String) -> String) {
 fun printString(string: String) = println(stringStrategy.invoke(string))
 } val lowerCasePrinter = Printer({ it.toLowerCase() })
 val prefixPrinter = Printer({ "Prefix: " + it })
 
 prefixPrinter.printString("Hello world") //Prefix: Hello world
 lowerCasePrinter.printString("HELLO WORLD") //hello world
57. Destructuring declarations data class User(val name: String, val age: Int,
 val city: String, val country: String)
58. Destructuring declarations data class User(val name: String, val age: Int,
 val city: String, val country: String) val user = User("Cristian", 31, "bcn", "Spain")
 val user2 = user.copy(city = "Madrid")
 
 val listFUsers = listOf(user, user2)
 
 for ((name, age, city, country) in listFUsers) {
 println("Hi! $name from $city, $country")
 }
 
 val (age) = user
 println("Hi $age") //Hi Cristian
59. Destructuring declarations data class User(val name: String, val age: Int,
 val city: String, val country: String) val salute = Pair("Hola", "Hi")
 println(salute.first)// Hola
 
 val (spanish, english) = salute
 println(spanish)// Hola val user = User("Cristian", 31, "bcn", "Spain")
 val user2 = user.copy(city = "Madrid")
 
 val listFUsers = listOf(user, user2)
 
 for ((name, age, city, country) in listFUsers) {
 println("Hi! $name from $city, $country")
 }
 
 val (age) = user
 println("Hi $age") //Hi Cristian
60. DSL fun main(args: Array<String>) = {
 val time = measureTimeMillis {
 doSomethingUsefulOne()
 }
 println("Completed in $time ms")
 }
61. DSL fun main(args: Array<String>) = {
 val time = measureTimeMillis {
 doSomethingUsefulOne()
 }
 println("Completed in $time ms")
 } inline fun measureTimeMillis(block: () -> Unit) : Long {
 val start = System.currentTimeMillis()
 block()
 return System.currentTimeMillis() - start
 }
62. DSL’s fun setListener(view: View) {
 view.setOnClickListener(View.OnClickListener {
 doSomething()
 })
 }
63. DSL’s fun setListener(view: View) {
 view.setOnClickListener(View.OnClickListener {
 doSomething()
 })
 } fun setListener(view: View) {
 view.setOnClickListener({ v -> doSomething() })
 }
64. DSL’s fun setListener(view: View) {
 view.setOnClickListener(View.OnClickListener {
 doSomething()
 })
 } fun setListener(view: View) {
 view.setOnClickListener({ v -> doSomething() })
 } fun setListener(view: View) {
 view.setOnClickListener({ doSomething() })
 }
65. DSL’s fun setListener(view: View) {
 view.setOnClickListener(View.OnClickListener {
 doSomething()
 })
 } fun setListener(view: View) {
 view.setOnClickListener({ v -> doSomething() })
 } fun setListener(view: View) {
 view.setOnClickListener({ doSomething() })
 } fun setListener(view: View) {
 view.setOnClickListener { doSomething() }
 }
66. DSL’s fun setListener(view: View) {
 view.setOnClickListener(View.OnClickListener {
 doSomething()
 })
 } fun setListener(view: View) {
 view.setOnClickListener({ v -> doSomething() })
 } fun setListener(view: View) {
 view.setOnClickListener({ doSomething() })
 } fun setListener(view: View) = view.setOnClickListener { doSomething() } fun setListener(view: View) {
 view.setOnClickListener { doSomething() }
 }
67. • Final classes • Companion objects • No checked exceptions • Annotations for java integration
68. Thanks! Any questions?