00. 目录

01. 限定修饰符介绍

repeated 代表可重复，我们可以理解为数组

syntax = "proto3";//指定版本信息，不指定会报错message Person //message为关键字，作用为定义一种消息类型
{string name = 1;    //姓名int32 id = 2;       //idstring email = 3;   //邮件
}message AddressBook
{repeated Person people = 1;
}

02. 字段API分析

deng@itcast:/mnt/hgfs/LinuxHome/day03$ protoc addressbook.proto --cpp_out=./
deng@itcast:/mnt/hgfs/LinuxHome/day03$ 

而对于字段修饰符为repeated的字段生成的函数，则稍微有一些不同，如people字段，则编译器会为其产生如下的代码：

  enum : int {kPeopleFieldNumber = 1,};  // repeated .Person people = 1;int people_size() const;private:int _internal_people_size() const;public:void clear_people();::Person* mutable_people(int index);::PROTOBUF_NAMESPACE_ID::RepeatedPtrField< ::Person >*mutable_people();private:const ::Person& _internal_people(int index) const;::Person* _internal_add_people();public:const ::Person& people(int index) const;::Person* add_people();const ::PROTOBUF_NAMESPACE_ID::RepeatedPtrField< ::Person >&people() const;

03. 测试代码

参考代码如下：

#include "addressbook.pb.h"
#include <iostream>
#include <fstream>using namespace std;void set_addressbook()
{AddressBook obj;Person *p1 = obj.add_people(); //新增加一个Personp1->set_name("tom");p1->set_id(1);p1->set_email("tom@qq.com");Person *p2 = obj.add_people(); //新增加一个Personp2->set_name("jim");p2->set_id(2);p2->set_email("jim@qq.com");Person *p3 = obj.add_people(); //新增加一个Personp3->set_name("abc");p3->set_id(3);p3->set_email("abc@qq.com");fstream output("pb.itcast", ios::out | ios::trunc | ios::binary);bool flag = obj.SerializeToOstream(&output);//序列化if (!flag){cerr << "Failed to write file." << endl;return;}output.close();//关闭文件
}void get_addressbook()
{AddressBook obj;fstream input("./pb.itcast", ios::in | ios::binary);obj.ParseFromIstream(&input);  //反序列化input.close(); //关闭文件for (int i = 0; i < obj.people_size(); i++){const Person& person = obj.people(i);//取第i个peoplecout << "第" << i + 1 << "个信息\n";cout << "name = " << person.name() << endl;cout << "id = " << person.id() << endl;cout << "email = " << person.email() << endl << endl;}
}int main()
{// Verify that the version of the library that we linked against is// compatible with the version of the headers we compiled against.GOOGLE_PROTOBUF_VERIFY_VERSION;set_addressbook(); //序列化get_addressbook(); //反序列化// Optional:  Delete all global objects allocated by libprotobuf.google::protobuf::ShutdownProtobufLibrary();return 0;
}

04. 编译和测试

编译和测试

deng@itcast:/mnt/hgfs/LinuxHome/day03$ g++  test.cpp addressbook.pb.cc `pkg-config --libs --cflags protobuf`
deng@itcast:/mnt/hgfs/LinuxHome/day03$ ./a.out 
第1个信息
name = tom
id = 1
email = tom@qq.com第2个信息
name = jim
id = 2
email = jim@qq.com第3个信息
name = abc
id = 3
email = abc@qq.comdeng@itcast:/mnt/hgfs/LinuxHome/day03$ 

05. 参考

官方参考文档:https://developers.google.cn/protocol-buffers/docs/reference/cpp-generated#repeatednumeric

测试代码下载：测试代码下载