Install:
1. install vim. https://blog.csdn.net/zs376957686/article/details/77833953
2. copy (.vimrc .ycm_extra_conf.py .dircolors) to your path ( ~/ )
3. open vim and install plugins: (vim :PluginInstall)
4. install YouCompleteMe: 
cd ~/.vim/bundle/YouCompleteMe
./install.py --clang-completer --go-completer
5. modify the ycm conf ~/.ycm_extra_conf.py to your C++ conf, like this:
flags = [
'-Wall',
'-Wextra',
'-Werror',
'-fexceptions',
'-DNDEBUG',
# THIS IS IMPORTANT! Without a "-std=<something>" flag, clang won't know which
# language to use when compiling headers. So it will guess. Badly. So C++
# headers will be compiled as C headers. You don't want that so ALWAYS specify
# a "-std=<something>".
# For a C project, you would set this to something like 'c99' instead of
# 'c++11'.
'-std=c++1z',
# ...and the same thing goes for the magic -x option which specifies the
# language that the files to be compiled are written in. This is mostly
# relevant for c++ headers.
# For a C project, you would set this to 'c' instead of 'c++'.
'-x',
'c++',
'-isystem',
'/usr/include/c++/7.3.0',
'-isystem',
'/usr/include',
'-isystem',
'/usr/local/include',
'-isystem',
'/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1',
'-isystem',
'/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include',
]