It's typical that you don't think about keeping track of the app version for a particular user. However, as the app grows in regard to the number of users and releases, you will soon face the problem of update issues and incompatibilities. For example, a user may run an old version of your app but all your backend APIs now expect new parameters from a newer app version. Therefore, you may want to think about a strategy to detect the app version locally in order to notify the users of an update requirement. This is also helpful if your backend processes differently for a specific app version.
The app which you are going to build is very simple. It will detect the current version and store the information in a service. This is a screenshot of the app:
