Make multiple replica of single ios app

I have 10 ios apps which have same UI and almost same functionality except minor changes.

I have completed one app and want to make other 9 app and also used some 3rd party libraries and made changes to them and made some my custom functions for app functionality.

My concern is that if i will get change for even one functionality , i have to make that change to other 9 apps.

What is the the best and fastest way except changing code in each file ?