C++排序数组是指向类的指针

Question

我正在尝试对包含价格的汽车数组进行排序，我似乎在对指向另一个类的数组进行排序时遇到了问题。当我尝试更改数组的顺序时出现“错误 C2106:‘=’:左操作数必须是左值”。

我附上了下面的代码。

我的排序功能。

void CarPool::Sort()
{
    const int MAXVAL = 9;
    int coun = countCars;
    double temp;
    bool swappedFlag = true;

    while (swappedFlag)
    {
        swappedFlag = false;
        for (int i = 0; i < countCars - 1; i++)
        {
            ptrToPool[i].getPrice();
            if (ptrToPool[i].getPrice()> ptrToPool[i + 1].getPrice())
            {
                temp = ptrToPool[i].getPrice();
                ptrToPool[i].getPrice() = ptrToPool[i + 1].getPrice(); //ERROR C2106
                ptrToPool[i + 1].getPrice() = temp; //ERROR C2106
                swappedFlag = true;
            }
        }
    }
}

汽车.cpp

#pragma once
#include "car.h"  // put the related header at the TOP of the list of   includes
#include <string>
#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;

Car::Car(string mName, string reg, double eng, double pri)
{
    // store the parameter values for this object private data
     ModelName = mName;
     Registration = reg;
     EngineSize = eng;
     Price = pri;
}

Car::Car()
{
// set up a value that shows the data not properly loaded
    ModelName = "Unspecified";
}

void Car::Load(ifstream& carFile)
{
    carFile>>ModelName>>Registration>>EngineSize>>Price;

}


void Car::Display()
{
    cout<<setfill(' ')<<setw(10)<<ModelName<<setfill(' ')<<setw(10)<<Registration;
    cout<<setfill(' ')<<setw(10)<<EngineSize<<setfill(' ')<<setw(10)<<Price<<endl;
}

double Car::Ratio() //how much it costs per cc of engine!
{
    return EngineSize/Price;
}

string Car::getRegistration()
{
    return Registration;
}

double Car::getPrice()
{
    return Price;
}

carpool.cpp(也是第一段代码中列出的函数)

#include "carpool.h"

#include <iostream>
#include <fstream>

using namespace std;

CarPool::CarPool()
{
    countCars=0; //for now
    name = "None";
}

CarPool::~CarPool()
{
    if (countCars>0)
    {
        delete [] ptrToPool;
    }
}

int CarPool::Load(string fromFilename)
{
    // assumes file starts with count of cars
    ifstream inFile(fromFilename);
    if (!inFile)
    {
        return -1; //oh dear no file to read
    }
    inFile>>countCars; //read the following number of cars
    ptrToPool = new Car[countCars];
    for (int i=0; i<countCars; i++)
    {
        ptrToPool[i].Load(inFile);
    }
    return 0; //successful!
}

汽车.h

#pragma once
#include <string>
using namespace std;

class Car
{
public:
    // see later for the bodies of the functions!
    Car(string mName, string reg, double eng, double pri);
    Car();
    void Load(ifstream& carFile);
    void Save(ofstream& carFile);
    void Display();
    string getRegistration();
    double getPrice();
    double Ratio(); //how much it costs per cc of engine!
    void setPrice(double pri);

private:
    string ModelName;
    string Registration;
    double EngineSize;
    double Price;
};

Answer 1

getPrice() 定义为返回 double 值:

double Car::getPrice()

现在，在以下语句中，您将收到错误 C2106，因为您试图将一个数字赋值(相对于一个变量):

ptrToPool[i].getPrice() = ptrToPool[i + 1].getPrice(); //ERROR C2106
ptrToPool[i + 1].getPrice() = temp; //ERROR C2106