c++ - 值(value)？通过引用传递时是错误的

Question

我对 C++ 不是很精通，所以当我编写程序时，我首先用 Java 编写它，这样我可以更好地理解并帮助将其转换为 C++这是代码:

里程表.h

    class Odometer
    {
    public:
     Odometer();
     int traveled(int mils);
     void report();
    private:
     int miles;
    };

里程表类:

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

    Odometer::Odometer(){ //just added
    miles = 0; //initializing
    }
    int Odometer::traveled(int mils){
    miles = miles + mils;
    return miles;
    }
    void Odometer::report(){
    int limit = 999999;
    if (miles < limit){
        cout << miles;
        }
    else{
        miles = 0;
    }
    }

电量计.h

    class FuelGauge{
     public:
      FuelGauge();
      int add(int gallons);
      void report();
      void decrement(int gallons);
     private:
      int gallons;
     };

电量计类

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

FuelGauge::FuelGauge(){ //just added 
gallons = 0;
}
int FuelGauge::add(int gals){
    gallons = gallons + gals;
    return gallons;
    }
void FuelGauge::report(){
    cout << gallons << endl;
    }
void FuelGauge::decrement(int galls){
    gallons = gallons - galls;
    }

CarInfoMain 类

#include "FuelGauge.h"
#include "Odometer.h"
#include <iomanip>
#include <iostream>
using namespace std;

int main(){
    FuelGauge g;
    Odometer m;
    int gallons;
    int miles;

    cout << "How many gallons do you want to start with in the car? " << endl;
    cin >> gallons;
    g.add(gallons);
    cout << "How far did you travel? " << endl;
    cin >> miles;
    g.decrement(miles / 24);
    cout << "Current Gallons now: " << endl;
    g.report(); //<--- this is where it doesn't return it right
    /*cout << "Odometer: " << endl;
    m.report();*/
}

样本运行:

Gallons started with? 14

Miles traveled? 150

Current gallons now: 1470880840 //usually a large number of this size, sometimes //with a minus in the front, e.g -574807128

我不知道为什么它不起作用。谢谢

Answer 1

在 C++ 中，局部变量默认具有垃圾值/(在为您的变量分配之前内存单元中的内容)。

所以当你计算 miles = miles + mils您正在为一些垃圾值(value)增加里程只需将英里和加仑初始化为 0 即可解决此问题。

int 英里 = 0;int 加仑 = 0;