single property
Checks that this iterable has only one element, and returns that element.
Throws a StateError if this
is empty or has more than one element.
This operation will not iterate past the second element.
Implementation
@override
T get single {
final l = length;
if (l > 1) {
throw RealmStateError('Too many elements');
}
if (l == 0) {
throw RealmStateError('No element');
}
return this[0];
}