Major Extension Function in Kotlin that I use it.

Scoping.kt

//This generic function mechanism similar to the `guard` statement in Swift but in Kotlin


inline fun <reified T> T?.guard(block: (T?) -> Nothing): T {
    return this ?: block(this)
}

//This generic function mechanism simillar to the `apply` difference is that returning Unit.

@OptIn(ExperimentalContracts::class)
inline fun <reified T> T.actually(block: T.() -> Unit) {
    contract {
        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
    }
    return block()
}

//This generic function mechanism simillar to the `let` difference is that returning Unit.

@OptIn(ExperimentalContracts::class)
inline fun <reified T> T.absolutely(block: (T) -> Unit) {
    contract {
        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
    }
    return block(this)
}