orElseGet method

If a value is present, returns the value, otherwise returns the result produced by the supplying function.

supplier the supplying function that produces a value to be returned

Returns the value, if present, otherwise the result produced by the supplying function.

Throws InvalidArgumentException if no value is present and the supplying function is null.

Example

Optional<String> name = Optional.of("Kate");
Optional<String> empty = Optional.empty();

print(name.orElseGet(() => "Generated")); // "Kate"
print(empty.orElseGet(() => "Generated")); // "Generated"

// Lazy evaluation - supplier only called when needed
String expensiveDefault() {
  print("Computing expensive default...");
  return "expensive result";
}

print(name.orElseGet(expensiveDefault)); // "Kate" (no print)
print(empty.orElseGet(expensiveDefault)); // "expensive result" (prints message)

// Useful for expensive computations
Optional<List<String>> cachedData = Optional.empty();
List<String> data = cachedData.orElseGet(() => loadDataFromDatabase());

// With random values
import 'dart:math';
Random random = Random();
Optional<int> maybeNumber = Optional.empty();
int number = maybeNumber.orElseGet(() => random.nextInt(100));