boost多索引容器的使用介绍

boost是基于C++11的被广泛使用的开源库；
多索引容器实现了可以通过多个索引去查找数据，不像std::map 一样 只能通过单一索引key查找对应value值。多索引容器可以通过多个索引key查找对应value值。多对多的方式，有了更多的应用场景。其实现了STL的一些基本操作，如迭代器等。如下示例作为对多索引容器的进一步了解。
boost编译见 https://blog.csdn.net/weixin_44328568/article/details/128011177

示例 multi_index.cpp：

#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>

#include <boost/multi_index_container.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/shared_ptr.hpp>

using namespace std; /* 项目里不要这样 */

/* 定义学生信息，同理可以使用结构定义 */
class student {
public:
        student(int id, string name, int score, string remark) :id(id), name(name), score(score), remark(remark) {
        }

        void print() const {
                cout << "\tid:" << id << "\tname:" << name << "\tscore:" << score << "\tremark:" << remark << endl;
        }
        int id;
        string name;
        int score;
        string remark;
};

/* 如果要把student某个属性字段设置为搜索引擎，则需要定义用于排序的空结构体对象 */
struct _id {};
struct _name{};
struct _score {};

/* 定义一个multi_index_container（多索引容器）*/
using student_table =
boost::multi_index::multi_index_container<
        student,
        boost::multi_index::indexed_by<
                boost::multi_index::ordered_unique<boost::multi_index::tag<_id>, BOOST_MULTI_INDEX_MEMBER(student, int, id)>,   // ID为唯一索引，类似主键
                boost::multi_index::ordered_non_unique<boost::multi_index::tag<_name>, BOOST_MULTI_INDEX_MEMBER(student, string, name)>, // 非唯一索引
                boost::multi_index::ordered_non_unique<boost::multi_index::tag<_score>, BOOST_MULTI_INDEX_MEMBER(student, int, score)>
        >
>;


void insertData( student_table &allStu ){
        allStu.insert(student(1, "lili", 85, "hello"));
        allStu.insert(student(2, "liming", 90, "hello"));
        allStu.insert(student(3, "xiaoming", 65, "hello"));
        allStu.insert(student(4, "ergou", 80, "hello"));
        allStu.insert(student(5, "dagou", 60, "hello"));
}
/* compile:  g++ -std=c++11 -I./include multi_index.cpp */
int main() {
        student_table allStu;

        insertData( allStu ); // 插入数据

        cout << endl << "-- sort by student id:" << endl << endl;
        for (auto &iter : allStu.get<_id>() ){ // get return of student_table::index<_id>::type&
                iter.print();
        }

        cout << endl << "-- sort by student name:" << endl << endl;
        for (auto &iter : allStu.get<_name>() ){ // get return of student_table::index<_name>::type&
                iter.print();
        }

        cout << endl << "-- sort by student score:" << endl << endl;
        for (auto &iter_score : allStu.get<_score>()) { // student_table::index<_score>::type&
                iter_score.print();
        }

        // find and modify
        auto &stu_of_name  = allStu.get<_name>(); // student_table::index<_name>::type
        auto iter_ergou = stu_of_name.find("ergou"); // student_table::index<_name>::type::iterator

        if ( iter_ergou != stu_of_name.end() ) {
                student ergou = *iter_ergou;
                ergou.score = 33;
                ergou.remark = "modified by program";
                bool isSuc = stu_of_name.replace(iter_ergou, ergou);
        }

        cout << endl << "-- sort by student id after replace ergou:" << endl << endl;
        for (auto &iter : allStu.get<0>() ){ // get return of student_table::index<_id>::type&
                iter.print();
        }

        cout << endl;
}

编译及结果：

-bash-4.2# ls
include  lib  multi_index.cpp
-bash-4.2# g++ -std=c++11 -I./include multi_index.cpp
-bash-4.2# ./a.out

-- sort by student id:

        id:1    name:lili       score:85        remark:hello
        id:2    name:liming     score:90        remark:hello
        id:3    name:xiaoming   score:65        remark:hello
        id:4    name:ergou      score:80        remark:hello
        id:5    name:dagou      score:60        remark:hello

-- sort by student name:

        id:5    name:dagou      score:60        remark:hello
        id:4    name:ergou      score:80        remark:hello
        id:1    name:lili       score:85        remark:hello
        id:2    name:liming     score:90        remark:hello
        id:3    name:xiaoming   score:65        remark:hello

-- sort by student score:

        id:5    name:dagou      score:60        remark:hello
        id:3    name:xiaoming   score:65        remark:hello
        id:4    name:ergou      score:80        remark:hello
        id:1    name:lili       score:85        remark:hello
        id:2    name:liming     score:90        remark:hello

-- sort by student id after replace ergou:

        id:1    name:lili       score:85        remark:hello
        id:2    name:liming     score:90        remark:hello
        id:3    name:xiaoming   score:65        remark:hello
        id:4    name:ergou      score:33        remark:modified by program
        id:5    name:dagou      score:60        remark:hello

-bash-4.2#