arrow-core/arrow.core.raise/ensureNotNull

ensureNotNull

inline fun <Error, B : Any> Raise<Error>.ensureNotNull(value: B?, raise: () -> Error): B

Ensures that the value is not null; otherwise, Raise.raises a logical failure of type Error.

In summary, this is a type-safe alternative to requireNotNull, using the Raise API.

Example

@JvmInline
 value class FullName(val name: String)

 sealed interface NameError {
     object NullValue : NameError
 }

 fun Raise<NameError>.fullName(name: String?): FullName {
     val nonNullName = ensureNotNull(name) { NameError.NullValue }
     return FullName(nonNullName)
 }

 fun main() {
     recover({
         fullName("John Doe") // valid
         fullName(null) // raises NameError.NullValue error
     }) { error ->
         // Handle errors in a type-safe manner
         when (error) {
             NameError.NullValue -> {}
         }
     }
 }

Parameters

value

the value that must be non-null.

raise

a lambda that produces an error of type Error when the value is null.