【iOS】duplicate symbols for architecture x86_64

今天遇到了这个问题，错误如下：

duplicate symbol _OBJC_IVAR_$_BCViewController.bank in:
    /Users/***/Library/Developer/Xcode/DerivedData/***-fmtpkcbvfajuuadtvwtzfyjxoywz/Build/Intermediates/***.build/Debug-iphonesimulator/***.build/Objects-normal/x86_64/BCViewController-56817B2065459D6D.o
    /Users/***/Library/Developer/Xcode/DerivedData/***-fmtpkcbvfajuuadtvwtzfyjxoywz/Build/Intermediates/***.build/Debug-iphonesimulator/***.build/Objects-normal/x86_64/BCViewController-B4FDBEBA5F30059F.o

ld: 11 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

网上有说是因为存在 同名的文件。刚开始没发现，后来仔细查找后果然是这个问题！！

PS: 这里是 BCViewController

参考：duplicate symbols for architecture armv7解决办法