Question

我一直得到三个与“调用隐式删除的____默认构造函数有关的错误。有人会碰巧知道这是为什么吗？

/ Users / vivekreddy / Desktop / Vivek / School / Spring 2016 / CS32 / project 3 / project 3 / Player.cpp:114:18：调用隐式删除的'BadPlayerImpl'默认构造函数

#include "provided.h"
#include <iostream>
#include <string>
using namespace std;



class HumanPlayerImpl:public Player
{
  public:
    virtual bool isInteractive() const { return true;};
    int chooseMove(const Scaffold& s, int N, int color);

};

class BadPlayerImpl: public Player
{
  public:
    int chooseMove(const Scaffold& s, int N, int color);
};

class SmartPlayerImpl: public Player
{
  public:
    virtual bool isInteractive() const { return true;};
    int chooseMove(const Scaffold& s, int N, int color);
};




//implementations


//put virtual in front of implementations only or declarations here as well?


int HumanPlayerImpl::chooseMove(const Scaffold& s, int N, int color)  //goal is to get N in a row, return the column necessary to put the checker so we could do that.  otherwise return -1.  can make the column be arbitrary
{
    //algorithm is inputting N so maybe don't need this check?
    if (N>s.cols()||N<=0) {
        cout<<"Enter a number within the valid range of columns you specified";
        return -1;
    }

    if(s.numberEmpty()==0)
    {
        return -1;
    }

    int columnnum;
    while (columnnum<=s.cols()||columnnum<=0) {
        cout<<"Enter column number of your move";
        cin>>columnnum;
        if (columnnum<=s.cols()) {
            return columnnum;
        }
        cout<<"Column number not valid ";
    }
    return -1; //OK?
}

int BadPlayerImpl::chooseMove(const Scaffold& s, int N, int color)
{
    if ((N>=s.cols()&&N>=s.levels())||N<=0) { //make sure this works
        cout<<"Enter a number within the valid range of columns you specified";
        return -1;
    }
    for (int j=0; j<s.cols();j++) {
        if (s.checkerAt(j,0)==VACANT) { 
            return j;
        }
    }
    return -1; //see if this OK
}

int SmartPlayerImpl::chooseMove(const Scaffold& s, int N, int color)
{
    return -1;  //  This is not always correct; it's just here to compile
}

//******************** Player derived class functions *************************

// These functions simply delegate to the Impl classes' functions.
// You probably don't want to change any of this code.

HumanPlayer::HumanPlayer(string nm)
 : Player(nm)
{
    m_impl = new HumanPlayerImpl;  //error is here
}

HumanPlayer::~HumanPlayer()
{
    delete m_impl;
}

int HumanPlayer::chooseMove(const Scaffold& s, int N, int color)
{
    return m_impl->chooseMove(s, N, color);
}

BadPlayer::BadPlayer(string nm)
 : Player(nm)
{
    m_impl = new BadPlayerImpl;  //error is here 
}

BadPlayer::~BadPlayer()
{
    delete m_impl;
}

int BadPlayer::chooseMove(const Scaffold& s, int N, int color)
{
    return m_impl->chooseMove(s, N, color);
}

SmartPlayer::SmartPlayer(string nm)
 : Player(nm)
{
    m_impl = new SmartPlayerImpl;  //error is here 
}

SmartPlayer::~SmartPlayer()
{
    delete m_impl;
}

int SmartPlayer::chooseMove(const Scaffold& s, int N, int color)
{
    return m_impl->chooseMove(s, N, color);
}

下面是我对类Player的声明，它是基类：

class Player
{
  public:
    Player(std::string nm) : m_name(nm) {}
    virtual ~Player() {};
    std::string name() const { return m_name; };
    virtual bool isInteractive() const { return false; }
    virtual int chooseMove(const Scaffold& s, int N, int color) = 0;
      // We prevent any kind of Player object from being copied or assigned by
      // making the copy constructor and assignment operator unavailable in
      // the base class (and thus in any derived class).
    Player(const Player& other) = delete;
    Player& operator=(const Player& other) = delete;
  private:
    std::string m_name;
};

Answer 1

因为您在基类中声明了一个构造函数，特别是Player::Player(std::string nm)，所以编译器不可能为您的子类提供隐式默认构造函数，因为您的父类Player不能是默认的首先建造。

在子类中提供构造函数或继承基类的构造函数（C ++ 11）。 E.g：

BadPlayerImpl::BadPlayerImpl(std:string nm)
  : Player(nm)
{
   ...
}

Answer 2

这很可能是因为代码中的某个地方是复制构造或分配给BadPlayerImpl的实例，并且您明确删除了其超类的复制构造函数和赋值运算符。

Answer 3

通常会为类自动创建默认构造函数，但是有关于何时不创建它的规则（例如，当您创建另一个构造函数时）。你在哪里＆＃34; //错误在这里＆＃34;你正在调用Sub-Class的默认构造函数，它将调用Base-Class的（在这种情况下，不存在的）默认构造函数。

“调用隐式删除的默认构造函数”错误

3 个答案: