ndefined symbols for architecture x86_64:

问题 ：文件删掉，重新导入，报“ndefined symbols for architecture x86_64:

"OBJC_CLASSKaTeX parse error: Expected group after '_' at position 103: …nt: _OBJC_CLASS_̲_goodListForExpandViewModel)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
”

原因：编译连接断开；

解决办法：Build Phases -Compile Sources -+进来