Mastering Kotlin

Smart casting

We can check whether a variable is of a particular type by using the is keyword. For example, we could check whether settingsProvider is an instance of SettingsManager as follows:

fun main(args: Array<String>) {    val settingsProvider: SettingsProvider = SettingsManager    if (settingsProvider is SettingsManager) {        // do something    }}

Conversely, you can check whether a variable is not of a certain type by using !is:

fun main(args: Array<String>) {    val settingsProvider: SettingsProvider = SettingsManager    if (settingsProvider !is SettingsManager) {        // do something    }}

The Kotlin compiler can track explicit casts and type checks and can perform smart casting for us. This means that, once the compiler has validated a variable's type, ...