xcode c++ 编程使用protobuf

1、我当前使用的mac OS系统是：

 macOS Mojave

Version 10.14.6

2、Command Line Tools：

Xcode Version 11.3.1 (11C504)

3、安装protobuf，

如果你愿意，可以选择源码安装，

我的开发环境采用port管理维护，所以port安装（Centos下使用yum，Ubuntu使用sudo apt-get），安装 protobuf-c protobuf3-cpp，执行命令:

macbook-pro:~ username$ sudo port install protobuf-c

--->  Computing dependencies for protobuf-c

The following dependencies will be installed:  protobuf3-cpp

Continue? [Y/n]: Y

--->  Fetching archive for protobuf3-cpp

--->  Attempting to fetch protobuf3-cpp-3.17.3_0.darwin_18.x86_64.tbz2 from https://pek.cn.packages.macports.org/macports/packages/protobuf3-cpp

--->  Attempting to fetch protobuf3-cpp-3.17.3_0.darwin_18.x86_64.tbz2.rmd160 from https://pek.cn.packages.macports.org/macports/packages/protobuf3-cpp

--->  Installing protobuf3-cpp @3.17.3_0

--->  Activating protobuf3-cpp @3.17.3_0

--->  Cleaning protobuf3-cpp

--->  Fetching archive for protobuf-c

--->  Attempting to fetch protobuf-c-1.4.0_0.darwin_18.x86_64.tbz2 from https://pek.cn.packages.macports.org/macports/packages/protobuf-c

--->  Attempting to fetch protobuf-c-1.4.0_0.darwin_18.x86_64.tbz2.rmd160 from https://pek.cn.packages.macports.org/macports/packages/protobuf-c

--->  Installing protobuf-c @1.4.0_0

--->  Activating protobuf-c @1.4.0_0

--->  Cleaning protobuf-c

--->  Scanning binaries for linking errors

--->  No broken files found.                             

--->  No broken ports found.

4、使用protobuf编程，