trySingleWhereOrDefault method

T? trySingleWhereOrDefault(
  1. bool condition(
    1. T element
    ), {
  2. T? defaultValue,
})

Returns the single element in the iterable matching a condition, or a defaultValue if no such element exists.

Iterates over the entire iterable, applying the condition function to each element. At the end of the iteration, if only a single element matches the condition, that element is returned. If no elements match the condition or if more than one element matches the condition, the value specified by defaultValue is returned instead,.

This method will short-circuit after finding a second element that matches the condition. In the worst-case scenario, this method will iterate over the entire iterable.

Example:

void main() {
  final list = [1, 2, 3];
  final result = list.trySingleWhereOrDefault((x) => x.isOdd, defaultValue: -1);

  // Result: -1
}

Implementation

T? trySingleWhereOrDefault(
  bool Function(T element) condition, {
  T? defaultValue,
}) {
  final iter = iterator;
  if (!iter.moveNext()) return defaultValue;

  T? val;
  var found = false;
  do {
    if (condition(iter.current)) {
      if (!found) {
        val = iter.current;
        found = true;
      } else {
        return defaultValue;
      }
    }
  } while (iter.moveNext());

  if (!found) return defaultValue;
  return val;
}