问题
When I run Convert to Obj-C it firsts runs a Precheck. Some files I want the Precheck to ignore, and I thought I could set the compiler flag -fno-objc-arc on those files. But Precheck phase seems to ignore that flag (and reset it)...so I don't really know how to get beyond Precheck.
回答1:
The first step of the pre-check has a list of all your files with checkboxes before them, just unstick the ones you do not want to convert to ARC, the migration tool will take care of setting the correct compiler flags during the conversion.
来源：https://stackoverflow.com/questions/7780412/how-do-i-convert-my-xcode-project-to-use-arc-automatic-reference-counting