What common idioms and patterns do you use in Kotlin?

In Kotlin, the following idioms and patterns are widely used, making the code more expressive and idiomatic:

• Using data classes for storing data with automatic generation of equals, hashCode, toString, and copy.

• Extension functions to add new methods to existing classes without inheritance.

• Lambda expressions and higher-order functions for convenient work with collections and asynchronous programming.

• Using sealed classes to express limited type hierarchies, which simplifies handling in when statements.

• Handling null-safety with operators ?., ?:, !!, and safe calls.

• Using coroutines for asynchronous and non-blocking programming.

• Idioms apply, let, run, also for convenient object configuration and call chains.

Example of using extension functions and data classes:

data class User(val name: String, val age: Int)

fun User.isAdult() = age >= 18

val user = User("Ivan", 20)
println(user.isAdult()) // true

These patterns help write clean, concise, and maintainable code in Kotlin.