gaplo917

#!/bin/sh
# install shit on mac osx
# author: mcor
# date: 2015-12-17

# install brew
ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

# install cask
brew tap caskroom/cask

gaplo917

// https://blog.gaplotech.com/content/images/2016/06/Screen-Shot-2016-06-22-at-22-09-29.png
// Result not consistent : 12291 false, 37709 true
for(var i=0; i<50000; ++i) {
	console.log(typeof null === 'undefined')
}
// OR
for(var i=0; i<50000; ++i) {
	console.log(typeof null == 'undefined')
}

gaplo917

//http://stackoverflow.com/questions/40398072/singleton-with-parameter-in-kotlin

class TasksLocalDataSource private constructor(context: Context) : TasksDataSource {

    private val mDbHelper: TasksDbHelper

    init {
        // You cannot pass null in kotlin unless you are using `context: Context?`
        // therefore, checking null is useless 
        // checkNotNull(context)

gaplo917

// Java null risk workaround example
// Kotlin null safe example https://gist.github.com/gaplo917/77d7ee9f48ed20f4a60bc20a1b39a2e6

import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.util.Optional;
import static java.lang.System.*;

class NullRisk {

gaplo917

// Kotlin null safe example
// Java null risk example https://gist.github.com/gaplo917/5dc037bedea39a348854ae59ba89c063

fun doSth(str: String): String {
    return str.toLowerCase()
}

fun doSthOptional(str: String?): String? {
    // Optional chainning, similiar to Swift
    return str?.toLowerCase()

gaplo917

// Java 9
final Map<String,Integer> abc = Map.of("a",1, "b", 2, "c", 3);

// Java >= 5
final Map<String,Integer> abc = new HashMap<String, Integer>() {{  
    put("a",1);
    put("b",2);
    put("c",3);
}};

gaplo917

// val abc: Map<String,Int> = mapOf("a" to 1, "b" to 2, "c" to 3)
// the actual type of the Map is obvious
// thus we can skip Map<String,Int> and let kotlin compiler to make type inference
val abc = mapOf("a" to 1, "b" to 2, "c" to 3)

val abcd = abc + ("d" to 4) // ok!
val abce = abc + ("e" to "5") // compile error: Type mismatch

// val c: Int? = abc["c"]
var c = abc["c"] 

gaplo917

// Java
// Ugly work around to save time (compared to method overload)
void doSomething(
  @NotNull String fname,
  @NotNull String lname,
  @Nullable String addr,
  @Nullable Gender gender
) {  
  requireNonNull(fname);
  requireNonNull(lname);

gaplo917

// Kotlin
// Default argument
fun doSomething(
  fname: String,
  lname: String,
  addr: String = "N/A",
  gender: Gender = Gender.Unknown
){
  // do something that really need fname,lname, addr, gender..
}

gaplo917

// Java 
// please focus on the function name & declaration 

// As we all know, String is a final class and we can't extend
class StringUtils{
  public static TypeA toTypeA(String str)
}

// Assume TypeA is from third party library that you can't extend
class TypeAUtils {