LearningKotlin

This summer I'm learning Kotlin for my future Android apps.
I'll be writing some .md files with the new things of kotlin I'm learning.
I'm using the kotlin official page reference to learn, so it could be very similar.
I'll put them here below 👇

Index

Packages
Functions
Variables
Conditional expressions
When Expression

Packages

The packages indicate the kotlin files folder
For example, in this project the folder src contains the folder main.
The folder main acts like a package.

All the functions of the files in main folder can be used in all the files without importing them.

Here's an example with code:

Main.kt

package main
// all the functions inside the package main can be used in other files in the same package without importing

fun main() {
    sum(1,2) // this function is in other file, but in the same package 
}

Functions.kt

package main // Is important to define the same package as the file where it's gonna be used

fun sum(number1: Int, number2: Int) = number1 + number2

Functions

The functions in kotlin can be written in two ways, if they return a value
For example:

fun sum(number1: Int, number2: Int) {
    return number1 + number2
}

Or simpler:

fun sum(number1: Int, number2) = number1 + number2

Also a function can be concatenated inside a string:

val number1 = 1
val number2 = 2

println("The sum of $number1 and $number2 is equal to ${sum(number1, number2)}")

Variables

The constants or variables read-only are defined with the keyword val as in this example:

val two = 2

The variables are defined with the keyword var. Here's an example:

var x = 0
x += 1

println(x)

Conditional Expressions

In Kotlin the conditional expressions are defined like this example:

fun maxOf(number1: Int, number2: Int) {
    if (number1 > number2) {
        return number1
    } else {
        return number2
    }
}

But it could be written simpler

fun maxOf(number1: Int, number2: Int) {
    return if (number1 > number2) {
        number1
    } else {
        number2
    }
}

But it could be written in the simpler way

fun maxOf(number1: Int, number2: Int) = if (number1 > number2) number1 else number2

When Expression

The when expression is used like the switch expression:

when(x) {
    1 -> "one"
    2 -> "two"
    3 -> "three"
    else -> "it's other number"
}

EddyBer16 / LearningKotlin