Question

我通过map:map reference at 。我所要做的是建立一个像以下地图:

std::map<TriSpec, unsigned int> TriSpecMap;

接着,我要插入如下内容:

result = TriSpecMap.insert(std::make_pair(triSpecObject, anUnsignedInt));

The following is a short example of my TriSpec Header and .cpp:

//TriSpec.h
#ifndef TRISPEC_H
#define TRISPEC_H
class TriSpec
{
public:
    TriSpec(void);
    ~TriSpec(void);

    unsigned int m_position;
};
bool operator< (const TriSpec& lhs, const TriSpec& rhs);
#endif

//TriSpec.cpp
#include "TriSpec.h"

TriSpec::TriSpec(void){}
TriSpec::~TriSpec(void){}

bool operator< (const TriSpec& lhs, const TriSpec& rhs)
{
    if (lhs.m_position < rhs.m_position) return true;
    else return false;
}

我超负荷了正确的运营商? 功能/配制Im是否正确? 当我看<代码>result.second时,它始终是true,即使我知道正在插入的物体已经存在于地图上。

Answer 1

我看不出贵国的法典有任何问题,但“蓝色经营者”应当是朋友(甚至没有朋友的关键词):

bool friend operator< (const TriSpec& lhs, const TriSpec& rhs)
{
     return (lhs.m_position < rhs.m_position);
}

然后按预期开展工作:

int main(int argc, _TCHAR* argv[])
{
    std::map<TriSpec, unsigned int> TriSpecMap;

    TriSpec triSpecObject1;
    triSpecObject1.m_position = 1;

    TriSpec triSpecObject2;
    triSpecObject2.m_position = 1;

    TriSpec triSpecObject3;
    triSpecObject3.m_position = 3;

    std::pair<std::map<TriSpec, unsigned int>::iterator, bool> retVal = 
        TriSpecMap.insert(std::make_pair(triSpecObject1, 1));

    retVal = TriSpecMap.insert(std::make_pair(triSpecObject2, 1));

    retVal = TriSpecMap.insert(std::make_pair(triSpecObject3, 1));

    return 0;
}

The result of first insertion is true, the result of second is false a the third is true again - as it should be. The map container contains two objects then - triSpecObject1 a triSpecObject3.

Answer 2

∗∗∗∗ 无论如何,不折抵价值。 (Edit:阁下,感谢) 您可以简化这一框架:

bool operator< (const TriSpec& lhs, const TriSpec& rhs)
 {
      return (lhs.m_position < rhs.m_position);
 }

由于你没有显示在地图上插入的完整的代码,因此无法说明返回价值编码为何。回返总是真实的。

Answer 3

自 C++11,你还可以使用lambda expression ,而不是提供operator<。因此,你只能绘制以下两条法典:

int main()
{
    auto comp = [](const TriSpec& t1, const TriSpec& t2) { return t1.m_position < t2.m_position; };
    std::map<TriSpec, unsigned int, decltype(comp)> TriSpecMap(comp);

    TriSpec t1, t2, t3;
    t1.m_position = 1;
    t2.m_position = 3;
    t3.m_position = 5;

    auto retVal = TriSpecMap.emplace(t1, 4);
    retVal = TriSpecMap.emplace(t2, 2);
    retVal = TriSpecMap.emplace(t3, 6);

    for (auto const &kv : TriSpecMap)
        std::cout << kv.first.m_position << ": " << kv.second << std::endl;

    return 0
}

产出:

1: 4
3: 2
5: 6

https://ideone.com/JbtrEL”rel=“nofollow noretinger”>Code on Ideone

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