I have an existing project, quite old, with its own support system: in-app purchases, links on web pages, etc.
I would like to overhaul the app significantly front and back end, so much so that basically none of the original code will remain. Maybe even write it in Swift instead of Objective-C, mostly because it's getting harder and harder to find Objective-C documentation.
Is it possible to set up the new app in Xcode so that for all intents and purposes, the app store just considers it to be a new version of the existing app? The in-app purchases work with it, the links to the app store still work, etc.
Yes, no problem. As long as the new app has the same bundle ID as the old app (CFBundleIdentifier in the Info.plist), it is the same app in the eyes of the App Store and Apple. You can change everything else about it and they won't care: icons, user-facing name (CFBundleDisplayName), underlying language, interface, major functionality even. The in-app purchases are attached to that bundle ID so they just keep on working; the links to the app store won't change. You can start a completely new project, from scratch, and as long as the bundle ID is the old bundle ID, it's the same app.
来源：https://stackoverflow.com/questions/56411310/swap-out-old-project-with-new-one