removeFirst method
T?
removeFirst()
删除第一个的元素, 并发射
Implementation
T? removeFirst() {
if (_subject.isClosed) {
L.w('IO在close状态下请求发送数据');
return null;
}
final T firstElement = latest!.first;
if (latest!.isNotEmpty) {
_subject.add(latest?..removeAt(0));
}
return firstElement;
}