Learning something new - Kotlin

Main: https://en.wikipedia.org/wiki/Kotlin_(programming_language)
Ref: https://medium.com/@mayuroks/learn-kotlin-for-android-in-one-day-50aa0bc099b0

Kotlin has been Google’s preferred language for Android app development since 7 May 2019.
I started working with Kotlin on 7 July 2019. That's 2 months of delay/gap.
I was busy traveling - Tokyo - Seattle - San Francisco - Tokyo - Mumbai - Delhi.

Now that i have settled in one place - Gurgaon, it's time to dive in.

History: Kotlin v1.0 was released on 15 February 2016.
It’s influenced by Java, Scala, Groovy, C#, Gosu, JavaScript, and Swift.

val : constant (immutable)
var : variable (mutable)

var username: String = "some user name"
val API_DELAY_CONSTANT: Int = 100

var myString: String? = null

fun getNumber(): Int {
return 1
}
private fun getStringLength(str1: String, str2: String): Int {
return str1.length + str2.length
}

var items: List<String> = ArrayList<String>()
for (item in items) {
// do something with item
}

for (index in items.indices) {
// access items using index
// items.get(index)
}

var i: Int = 0
// Some while loop
do {
    // do something
    i++

} while (i < 5)
// Another while loop
while (i < 10) {
    // do something
    i++


}

// A cool example of when statement
fun describe(obj: Any): String? {
var res: String? = null

when (obj) {
1 -> { res = "One" } // if obj == 1
"Hello" -> res ="Greeting" // if obj == "Hello"
is Long -> "Long" // if obj is of type Long
!is String -> "Not string" // if obj is not of type String
else -> {
// execute this block of code
}
}

return res
}


Kotlin has support for nested functions wow!

All nullable objects must be declared with a "?" postfix after the type name. Operations on nullable objects need special care from developers: null-check must be performed before using the value. Kotlin provides null-safe operators to help developers:
1. A safe navigation operator "?."
2. A null coalescing operator "?:" named Elvis operator after Elvis Presley

foo()?.bar()?.baz().

Android Studio (based on IntelliJ IDEA) has official support for Kotlin, starting from Android Studio 3.
link: https://developer.android.com/kotlin/index.html

Apps built with Kotlin:

1. Slack
2. Lyft
3. Robinhood
4. Evernote
5. Square
6. Deliveroo
7. Periscope
8. Udacity
9. Instacart
10. Pinterest
11. Basecamp
12. Pocket
13. Reddit
14. Camera360
15. Trello
16. Foursquare
17. Stride
18. Amex
19. Expedia
20. Netflix
21. Kindle
22. KeepSafe
23. NYTimes
24. Wordpress
25. Simple Bank
26. Twitter
27. Airbnb
28. Flipboard
29. Foursquare Robin
30. Tencent WeChat
31. GoJek
32. Confluence
33. June
34. Adobe Reader
35. Zomato

30 minutes to Learn Kotlin : https://developer.android.com/kotlin/learn

Developer Story - Zomato : https://www.youtube.com/watch?v=ao9QvtpszOU