Question

我有一个有两个班级的课程。在fileTxt类中，我声明x＆amp; y值和相对指针。然后我去Byz课，我宣布delta x＆amp; y值总和为x＆amp; y先前声明的值。然后程序回到fileTxt类我打印新的x＆amp; y值。
1）为什么x＆amp;在dx / dy sum之前的Byz类内的y值与x＆amp;是声明？
2）为什么新的x＆amp; y值是声明的而不是x / y里面的byz + dx / dy值？

main.cpp中

#include "fileTxt.h"
#include <iostream>

using namespace std;

int main()
{
    fileTxt _fileTxt;
    _fileTxt.elab();

    return 0;
}

fileTxt.cpp

#include "fileTxt.h"
#include "byz.h"
#include <iostream>
#include <string>
#include <cstdlib>

fileTxt::fileTxt()
{

}

fileTxt::~fileTxt()
{
    delete[] pX;
    pX=nullptr;
    delete[] pY;
    pY=nullptr;
}

void fileTxt::elab()
{
    x=12.34;
    y=56.78;
    std::cout << "x declaration: " << *pX << std::endl;
    std::cout << "y declaration: " << *pY << std::endl;

    Byz _Byz;
    _Byz.leggiByz();

    std::cout << "\nnew x value: " << *pX << std::endl;
    std::cout << "new y value: " << *pY << std::endl;
}

fileTxt.h

#ifndef FILETXT_H
#define FILETXT_H
#include <string>

class fileTxt
{
    public:
        fileTxt();
        virtual ~fileTxt();

        void elab();

    private:

        float x=0.0;
        float y=0.0;
        float *pX=&x;
        float *pY=&y;
};

#endif // FILETXT_H

byz.cpp

#include "byz.h"
#include <string>
#include <iostream>

Byz::Byz()
{

}

Byz::~Byz()
{

}

void Byz::leggiByz()
{
    dx=8.123;
    dy=9.456;

    std::cout << "\nx inside byz - before: " << *pX << std::endl;
    std::cout << "y inside byz - before: " << *pY << std::endl;
    std::cout << "\ndx: " << dx << std::endl;
    std::cout << "dy: " << dy << std::endl;
    *pX=*pX+dx;
    *pY=*pY+dy;
    std::cout << "\nx inside byz + dx: " << *pX << std::endl;
    std::cout << "y inside byz + dy: " << *pY << std::endl;
}

byz.h

#ifndef BYZ_H
#define BYZ_H
#include <string>

class Byz
{
    public:
        Byz();
        virtual ~Byz();

        void leggiByz();

    private:
        float dx=0.0;
        float dy=0.0;
        float x=0.0;
        float *pX=&x;
        float y=0.0;
        float *pY=&y;
};

#endif // BYZ_H

x声明：12.34
y声明：56.78

x里面byz - 之前：0.0
y by byz - 之前：0.0

dx：8.123
dy：9.456

x里面byz + dx：8.123
在里面byz + dy：9.456

新的x值：12.34
新y值：56.78

不同类中的成员/指针不会更改值

0 个答案: