filterItem method
按条件过滤, 并发射过滤后的数据
Implementation
List<T>? filterItem(bool Function(T element) test) {
if (_subject.isClosed) {
L.w('IO在close状态下请求发送数据');
return null;
}
final List<T> filtered = latest.where(test).toList();
_subject.add(filtered);
return filtered;
}