The named parameter 'initial' isn't defined.when using ValueGetter

/// Interface of an observable value of type [T]

abstract class RxValue implements Listenable {

factory RxValue(T initial) => StoredValue(initial);

factory RxValue.proxy(ValueGetter getterProxy) =>

  ProxyValue<T>(getterProxy);

/// Get current value

T get value;

/// Set value

set value(T val);

/// Cast [val] to [T] before setting

void setCast(dynamic /* T */ val);

}

the problem is when i call to other dart.file

final RxValue _user = RxValue(initial: null);

getting error :slight_smile:
“The named parameter ‘initial’ isn’t defined”