Please keep a copy of Xcode 6.1 before you upgrade to 6.2 via app store updates. Or download a copy of the older version from Apple's developer website.
It's really annoying to get Xcode 6.2 installed by App Store and discover that Xcode 6.1 is required for Xojo 2015r1 to build iOS apps.
If you install Xcode 6.1 in Applications folder you can switch with xcode-select command just like this:
sudo xcode-select -switch /Applications/Xcode\ 6.1.app
Just curious here after switching back to 6.2, the Xojo 2015r1 IDE still finds the simulator!
Earlier today it complained about missing iPhone SDK.