description

# singleWhere method Null safety

E singleWhere (

1. bool test(
   1. E element
   ),
2. {E orElse(
   )}

)
override

Returns the single element that satisfies `test`.

Checks elements to see if `test(element)` returns true. If exactly one element satisfies `test`, that element is returned. If more than one matching element is found, throws StateError. If no matching element is found, returns the result of `orElse`. If `orElse` is omitted, it defaults to throwing a StateError.

## Implementation

    E singleWhere(bool test(E element), {E Function()? orElse}) {
      late E result;
      bool foundMatching = false;
      for (E element in this) {
        if (test(element)) {
          if (foundMatching) {
            throw IterableElementError.tooMany();
          }
          result = element;
          foundMatching = true;
        }
      }
      if (foundMatching) return result;
      if (orElse != null) return orElse();
      throw IterableElementError.noElement();
    }