c通过引用将地图传递给函数

发布时间：2020-12-16 05:38:40 所属栏目：百科来源：网络整理

导读：如何通过引用将地图传递给函数？ Visual Studio 2010给我一个未解决的外部错误.目前,我有以下简化代码： void function1(){ mapint,int * my_map = new mapint,int(); function2(*my_map); }void function2(mapint,int temp_map){ //do stuff with the map}

如何通过引用将地图传递给函数？ Visual Studio 2010给我一个未解决的外部错误.目前,我有以下简化代码：

void function1(){
    map<int,int> * my_map = new map<int,int>(); 
    function2(*my_map); 
}

void function2(map<int,int> &temp_map){
    //do stuff with the map
}

这里有类似问题的几个答案,但是他们使用typedef并将std ::添加到定义的开头,但我真的不知道为什么.

int ComputerPlayer::getBestMoves(){
    //will return the pit number of the best possible move. 

    //map to hold pit numbers and rankings for each possible pit number.
    //map<pitNumber,rank> only adds pit numbers to map if they have seeds in them.

    std::map<int,int> possiblePits; //map
    std::map<int,int>::iterator it; //iterator for map
    for(int index = 1; index <= getBoardSize(); index++){
        if(_board.getPitValue(index) > 0){
            possiblePits.insert( pair<int,int>(index,0) ); 
        }
    }

    int tempBoardSize = _board.getBoardSize();

    //loop that will analyze all possible pits in the map
    for(it = possiblePits.begin(); it != possiblePits.end(); it++){
        Board tempBoard = _board;
        int pitNum = it->first; 

        int score = analyzePlay(pitNum,tempBoard,possiblePits);
    }
    return 0; 
}

int analyzePlay(int pitNum,Board tempBoard,std::map<int,int> &possibleMoves){
    int tempBoardSize = tempBoard.getBoardSize(); 
    int tempSeeds = tempBoard.getPitValue(pitNum);
    int lastPitSown; 

    tempBoard.setPitToZero(pitNum); 

    for(int index = 1; index <= tempSeeds; index++){

        if(pitNum == tempBoardSize * 2 + 1){
            //skips over human's score pit 
            pitNum += 2; 
            lastPitSown = pitNum;
            tempBoard.incrementPit(pitNum);
        }
        else{
            pitNum++;
            lastPitSown = pitNum;
            tempBoard.incrementPit(pitNum);
        }
    }

    if(tempBoard.getPitValue(lastPitSown) == 1 && lastPitSown >= tempBoardSize + 2 && lastPitSown <= tempBoardSize * 2 + 1){
        //turn ends. last seed sown into empty pit on opponent side. 

    }
    else if(tempBoard.getPitValue(lastPitSown) > 1 && lastPitSown != tempBoardSize + 1){
        //keep playing with next pit. last seed was sown into non-empty pit. 

    }
    else if(lastPitSown == tempBoardSize + 1){
        //extra turn. last seed sown into score pit.

    }
    else if(tempBoard.getPitValue(lastPitSown) == 1 && lastPitSown != tempBoardSize + 1 && lastPitSown <= tempBoardSize && lastPitSown >= 1 ){
        //turn ends. last seed sown into empty pit on your side. capture.


    }
    return 0;
}

我得到的错误：

Error   1   error LNK2019: unresolved external symbol "public: int __thiscall ComputerPlayer::analyzePlay(int,class Board,class std::map<int,int,struct std::less<int>,class std::allocator<struct std::pair<int const,int> > > &)" (?analyzePlay@ComputerPlayer@@QAEHHVBoard@@AAV?$map@HHU?$less@H@std@@V?$allocator@U?$pair@$$CBHH@std@@@2@@std@@@Z) referenced in function "public: int __thiscallComputerPlayer::getBestMoves(void)" (?getBestMoves@ComputerPlayer@@QAEHXZ)    C:UsersJoshDropboxCongkak_2Congkak_2ComputerPlayer.obj
Error   2   error LNK1120: 1 unresolved externals   C:UsersJoshDropboxCongkak_2DebugCongkak_2.exe

解决方法

两件事情：

>添加#include< map>在顶部,并使用std :: map而不是地图.
>定义function2上面的function1或者至少在function1上面声明function2.

以下是两个方面的做法：

#include<map>

void function2(std::map<int,int> &temp_map); //forward declaration

void function1(){
    std::map<int,int>  my_map; //automatic variable 
                                //no need to make it pointer!
    function2(my_map); 
}

void function2(std::map<int,int> &temp_map){
    //do stuff with the map
}

还要注意,尽可能避免新的.默认使用自动变量,除非你有很强的理由不使用它.

自动变量很快,代码看起来整齐干净.使用它们,更容易编写异常安全的代码.

编辑：

现在当你发布错误,你也意识到,

I forgot to add the Class that the function was part of to the beginning of it. as in: Player::function2(std::map<int,int> &temp_map){}

正如您在评论中所说.

很好,你自己弄清楚了.但是,当您提出问题时,始终将错误发布在您的第一篇文章中.记住这一点.

（编辑：李大同）

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