c++ - 通过迭代器为映射成员赋值

Question

我正在尝试遍历 map 并为其中的元素分配一个值:

typedef map<int,Node, less<int> >::const_iterator TopologyIter;

bool
RoutingManager::ActivateNewNode()
{
    TopologyIter iter;
    do
    {
        if(!iter->second.online)
        {
            iter->second.online = true;
            iter->second.connection = myConnection->newConnections.back();
            myConnection->newConnections.pop_back();
            return true; //all good
        }       

        iter++;

    }while (iter != topology.end());

    return false; //received a connection, but no more nodes to hand out
}

但是，我收到以下错误:

manager.cpp:91:24: error: assignment of member ‘Node::online’ in read-only object iter->second.online = true;

这是我的节点结构:

#pragma once

#include <map>
#include "nodecon.h"
typedef map<int,int, less<int> >::const_iterator NodeNeighborsIter;

struct Node
{
    int id;
    std::map<int,int> neighbors;
    bool online;

    struct NodeConnection connection;
};

我在这里错过了什么？

Answer 1

const_iterator 不能用于修改容器的内容。通过取消引用 const_iterator 获得的所有值都是 const。