Kotlin: Smart Casts - devrath/KotlinAlchemy GitHub Wiki

What is Smart casting

• Smart casting refers to the automatic casting of a variable to a certain type when a condition is met
• This helps to streamline the code and improve the type of safety
• It helps to avoid specific types of safety checks

Use case - 1

• The most common scenario for smart casting in Kotlin is with is checks.
• When you use the is operator to check if a variable is of a certain type, and the check passes, Kotlin automatically casts the variable to that type within the scope where the check is true. code

fun printStringLength(value: Any) {
    if (value is String) {
        // Inside this block, 'value' is automatically cast to String
        println("Length of the string is ${value.length}")
    } else {
        println("Not a string")
    }
}

Use case - 2

In the when expression, each branch with an is check results in smart casting of value to the corresponding type within that branch.

fun processValue(value: Any) {
    when (value) {
        is String -> println("Processing string: ${value.length}")
        is Int -> println("Processing integer: $value")
        else -> println("Unknown type")
    }
}