用 OC 很少的人去查了一下何为 Objective-C++，然后在 stackoverflow 发现一个 10 年前的问题，回答很有意思。
Objective-C++ is simply source code that mixes Objective-C classes and C++ classes (two entirely unrelated entities). Your C++ code will work, just as before, and the resulting executable will be linked with the Objective-C runtime, so your Objective-C classes will work as well. You can definitely use it in Xcode -- name your files with the .mm extension.
Also, you might want to read Apple's (sadly deleted, but archived) documentation on Objective-C++.
, answered Sep 10 '10