C ++无法从类中检索私有变量[关闭]

Posted 2023-02-22

【中文标题】C ++无法从类中检索私有变量[关闭]

【英文标题】：C++ Can't retrieve private variable from class [closed]

【发布时间】：2020-05-27 17:13:47

【问题描述】：

我正在编写一个程序来生成整数并设置用户选择的范围。

例如：

Enter the number of integers: 4 
Range: 10

4 9 2 1 are generated 现在用户一次选择 4 个数字，直到它们正确为止。 程序还会告诉用户他们是否部分正确。 例如：

User input: 4 9 0 7

Console << 2 of your answers are correct.

我有三个文件： 驱动程序.cpp

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

using namespace std;

int main()

    // Declare variables.
    Guess guess;
    int numberOfIntegers;
    int rangeOfIntegers;
    int count = guess.getSum();
    //Prompt user input.
    while(count != numberOfIntegers) 
        cout << "Enter the Number of Integers (n): " << endl;
        cin >> numberOfIntegers;
        cout << "Number of Each Integers from 1 to (m): " << endl;
        cin >> rangeOfIntegers;
        cout << "Enter your guesses for the " << numberOfIntegers << " integers in the range from 1 to " << rangeOfIntegers << " that have been selected:" << endl;
        guess.beginGuessingGame(rangeOfIntegers, numberOfIntegers);
    
     if (count == numberOfIntegers) 
            cout << "You are correct! Play again? (y/n)";
        
        else 
            cout << count << " of your guesses are correct." << endl;
        

;

游戏.h

// identifiers
#ifndef guessing_game
#define guessing_game

class Guess

     private :
          int * generatedSequence;
          int * inputGuess;
          int sum;
     public :
          void generateSequence(int inputRangeOfIntegers, int inputNumberOfIntegers);
          void beginGuessingGame(int inputRangeOfIntegers, int inputNumberOfIntegers);
          int getSum() 
              return sum;
          
;
#endif

和 Game.cpp

#include <iostream>

#include <iomanip>

#include "Game.h"

using namespace std;

void Guess::generateSequence(int inputRangeOfIntegers, int inputNumberOfIntegers) 
  /// Initialize random number generator.
  srand(time(0));

  /// Declare array size for the generated sequence to be based on user input.
  generatedSequence = new int[inputRangeOfIntegers];

  /// Input randomly generated numbers from from 0 to input range into generatedSequence.
  for (int i = 0; i < inputNumberOfIntegers; i++) 
    generatedSequence[i] = rand() % inputRangeOfIntegers + 1;
    cout << generatedSequence[i] << " " << endl;
  


void Guess::beginGuessingGame(int inputRangeOfIntegers, int inputNumberOfIntegers) 
  /// Call our generateSequence function.
  generateSequence(inputRangeOfIntegers, inputNumberOfIntegers);

  /// Declare guess size based on user input.
  inputGuess = new int[inputNumberOfIntegers];

  /// Begin endless loop for user to guess integers.
  for (;;) 
    for (int i = 0; i < inputNumberOfIntegers; i++) 
      cin >> inputGuess[i];
    

    /// If the user has found the random sequence, we can make sum equal to the number of integers.
    sum = 0;
    for (int i = 0; i < inputNumberOfIntegers; i++) 
      for (int j = 0; j < inputNumberOfIntegers; j++) 
        /// If the user has entered the right guess, we can tally sum to the number of integers entered.
        if (generatedSequence[i] == inputGuess[j]) 
          sum++;
          break;
        
      
    
  

我的问题是：我无法在主类中检索 sum 变量来检查它与整数的数量。因为如果它们相等，那么程序就知道用户猜对了。调用 beginGuessingGame 函数后我也无法使用 cout..

有什么建议吗？

谢谢。

【问题讨论】：

你为什么要制作一些你想从课堂之外访问的东西private？

@ScottHunter 作业指出我们必须使用“数据隐藏”。这会是个例外吗？

为什么不能使用getSum？

【参考方案1】：

至少这部分程序

Guess guess;
int numberOfIntegers;
int rangeOfIntegers;
int count = guess.getSum();

//Prompt user input.
while(count != numberOfIntegers)     //...

没有意义。该程序具有未定义的行为。

类对象guess的数据成员未初始化所以成员函数getSum返回对象的数据成员sum的不确定值。并且这个不确定值在while循环中与未初始化变量numberOfIntegers的另一个不确定值进行比较。

在函数generateSequence 中，此语句似乎有错字

generatedSequence = new int[inputRangeOfIntegers];

应该有

generatedSequence = new int[inputNumberOfIntegers];

在函数beginGuessingGame中有一个无限循环

  for (;;) 
    for (int i = 0; i < inputNumberOfIntegers; i++) 
      cin >> inputGuess[i];
    

    /// If the user has found the random sequence, we can make sum equal to the number of integers.
    sum = 0;
    for (int i = 0; i < inputNumberOfIntegers; i++) 
      for (int j = 0; j < inputNumberOfIntegers; j++) 
        /// If the user has entered the right guess, we can tally sum to the number of integers entered.
        if (generatedSequence[i] == inputGuess[j]) 
          sum++;
          break;
        
      
    
  

【讨论】：

改成while(true)，结果一样。

@xigedi20 请参阅我的附加帖子。而且您在 main 中的代码没有意义。例如，变量计数未初始化。因此，请选择最佳答案关闭此问题并重新编写程序，同时考虑到我在答案中写的内容。