(getRootNav) is deprecated and will be removed in the next major release. Use getRootNavById instead.
my current code is
this.app.getRootNav().setRoot(BootScreen);
plesese tell me how to set root using getRootNavById
Some solutions were provided in this duplicate question
https://forum.ionicframework.com/t/getrootnav-deprecated-use-getrootnavbyid-whats-the-value-of-the-root-nav-id?source_topic_id=115443