watch method
Watch all observables for changes.
Whenever any observable notifies of a change, the context
will
be rebuilt.
Returns current values for each observable.
It is safe to call this method multiple times within the same build method.
Implementation
(AsyncSnapshot<T0>, AsyncSnapshot<T1>) watch(BuildContext context) =>
($1.of(context).watch(context), $2.of(context).watch(context),);