Android Development with Kotlin

Crossinline modifier

Sometimes we need to use function type parameters from inline functions not directly in the function body, but in another execution context, such as a local object or a nested function. But standard function type parameters of inline functions are not allowed to be used this way because they allow non-local returns, which should not be allowed if this function could be used inside another execution context. To inform the compiler that non-local returns are not allowed, this parameter must be annotated as crossinline. Then it will act like a substitution that we are expecting in an inline function, even when it is used inside another lambda expression:

 fun boo(f: () -> Unit) { //... } inline fun foo(crossinline f: () ...