Xcode 6 and Xcode 7 are not supported by Apple on macOS Sierra, and should not be used for production work.
But what if you have a good reason for running one or the other? Maybe you want to compare a behavior in the latest Xcode 8 with an earlier version of the app. Instead of keeping a virtual machine around, or a second partition with an older OS release, it is liberating to be able to run and test against older versions of Xcode.
So far, it appears that Xcode 7 “mostly works” in spite of being unsupported by Apple. I’ve run into some launch-time crashes, but reopening the app tends to succeed.
Xcode 6 will flat out fail to launch, because one of its internal plugins depends on a private framework (Ubiquity.framework) that is no longer present on macOS Sierra. If you were willing to hack a copy of Xcode 6, however, you could get it running. You definitely shouldn’t do this, but if you’re curious how it could be done, here’s how:
- Always have a backup copy of any data that is important to you.
- Locate a copy of /System/Library/PrivateFrameworks/Ubiquity.framework from the previous OS X release.
- Copy the framework to within Xcode 6’s own Contents/Frameworks bundle subfolder:
ditto /my/old/System/Library/PrivateFrameworks/Ubiquity.framework ./Xcode.app/Contents/Frameworks/Ubiquity.framework
- Navigate to the problematic Xcode plugin and modify its library lookup table so that it points to the app-bundled copy of Ubiquity.framework, instead of the non-existent system-installed copy.
cd Xcode.app/Contents/PlugIns/iCloudSupport.ideplugin/Contents/MacOS install_name_tool -change /System/Library/PrivateFrameworks/Ubiquity.framework/Versions/A/Ubiquity @rpath/Ubiquity.framework/Versions/A/Ubiquity ./iCloudSupport
- Now that you've modified Xcode, its code signature is invalid. You can repair it by signing it with your own credentials or with an ad hoc credential:
codesign --deep -f -s - ./Xcode.app
- Did I mention you really shouldn't do this?
Apple has good reason to warn people off running older versions of Xcode, but if you absolutely need to get something running again, it's often possible.