升级XCode 10.2 之后突然发现添加文档注释无效 
怎么都按不出来
解决:
stackoverflow - https://stackoverflow.com/questions/47101437/add-documentation-is-disabled-in-xcode-9-1-9b55
As KellyTheDude mentioned, renaming or moving the Xcode.app will fix the issue on OSX 10.13 (High Sierra) since /usr/libexec/xpccachectl (the preferred solution) does not seem to exist under this version of the OS. To fix quickly:
Rename Xcode in the applications folder temporarily.
Name it back to Xcode
UPDATE: This fix also works on macOS Mojave (10.14) and Xcode 10
将Xcode临时修改名字 然后修改完之后再改回来即可~
