Binds an existing Stream<T> to this Rx to keep the values in sync.
You can bind multiple sources to update the value.
Closing the subscription will happen automatically when the observer
Widget (GetX or Obx) gets unmounted from the Widget tree.
updates the value to null and adds it to the Stream.
Even with null-safety coming, is still an important feature to support, as
call() doesn't accept null values. For instance,
InputDecoration.errorText has to be null to not show the "error state". [...]
Following certain practices on Rx data, we might want to react to certain
listeners when a value has been provided, even if the value is the same.
At the moment, we ignore part of the process if we .call(value) with
the same value since it holds the value and there's no real
need triggering the entire process for the same value inside, but
there are other situations where we might be interested in
triggering this. [...]