onData method

void onData (void handleData(T data))
override

Replaces the data event handler of this subscription.

The handleData function is called for each element of the stream after this function is called. If handleData is null, further elements are ignored.

This method replaces the current handler set by the invocation of Stream.listen or by a previous call to onData.

Implementation 

void onData(void handleData(T data)) {
  _source.onData(handleData);
}