程序抛出异常。认为这是由于动态数组没有以正确的容量构建所致

Question

我正在为学校编写一个项目，其中不允许使用任何外部库（这真的很糟糕，因为我必须根据项目要求制作动态数组而不是向量）。我相信问题是当我为动态数组运行构造函数时，它没有为我的数组分配容量。贝娄是我的构造函数。

Roster::Roster(int capacity) {
    capacity = capacity;
    size = 0;
    Student* classRosterArray = new Student[capacity];

然后我在主函数中使用

Roster classRosterArray(5);

来调用它。当我查看调试时，它显示 classRosterArray 的容量等于 0。我查看了其他人为作业所做的事情，他们做了

Roster::Roster(int capacity) {
    this->capacity = capacity;
    this->size = 0;
    this->classRosterArray = new Student * [capacity];

但是即使当我尝试它在调试中仍然说容量为 0 并且仍然抛出异常，输出中唯一的区别是它指定的 this 是 0xFDFDFE75 （尝试在两侧做两个星号，但是只是粗体）我认为这只是程序试图放入没有任何容量的数组中的指针。我对 C++ 还很陌生，这些指针一直让我感到非常痛苦。我将把所有代码放在下面，以防它不是我想的那样，但从我所有的调试和返工来看，这似乎是断点。

主.cpp

#include <iostream>
#include "degree.h"
#include "student.h"
#include "roster.h"
using namespace std;

int commaSpotStart = 0;
int commaSpotEnd;
int commaDist;
string scrubbedID;
string scrubbedFName;
string scrubbedLName;
string scrubbedEmail;
string scrubbedAge;
string scrubbedD1;
string scrubbedD2;
string scrubbedD3;
string scrubbedDegree;
int convAge;
int convD1;
int convD2;
int convD3;
DegreeProgram convDegree;


void scrub(string stringStudent) {
    commaSpotStart = 0;
    commaSpotEnd = stringStudent.find(",", commaSpotStart);
    scrubbedID = stringStudent.substr(commaSpotStart, commaSpotEnd);
    commaSpotStart = commaSpotEnd + 1;
    commaSpotEnd = stringStudent.find(",", commaSpotStart);
    commaDist = commaSpotEnd - commaSpotStart;
    scrubbedFName = stringStudent.substr(commaSpotStart, commaDist);
    commaSpotStart = commaSpotEnd + 1;
    commaSpotEnd = stringStudent.find(",", commaSpotStart);
    commaDist = commaSpotEnd - commaSpotStart;
    scrubbedLName = stringStudent.substr(commaSpotStart, commaDist);
    commaSpotStart = commaSpotEnd + 1;
    commaSpotEnd = stringStudent.find(",", commaSpotStart); commaDist = commaSpotEnd - commaSpotStart;
    scrubbedEmail = stringStudent.substr(commaSpotStart, commaDist);
    commaSpotStart = commaSpotEnd + 1;
    commaSpotEnd = stringStudent.find(",", commaSpotStart);
    commaDist = commaSpotEnd - commaSpotStart;
    scrubbedAge = stringStudent.substr(commaSpotStart, commaDist);
    commaSpotStart = commaSpotEnd + 1;
    commaSpotEnd = stringStudent.find(",", commaSpotStart);
    commaDist = commaSpotEnd - commaSpotStart;
    scrubbedD1 = stringStudent.substr(commaSpotStart, commaDist);
    commaSpotStart = commaSpotEnd + 1;
    commaSpotEnd = stringStudent.find(",", commaSpotStart);
    commaDist = commaSpotEnd - commaSpotStart;
    scrubbedD2 = stringStudent.substr(commaSpotStart, commaDist);
    commaSpotStart = commaSpotEnd + 1;
    commaSpotEnd = stringStudent.find(",", commaSpotStart);
    commaDist = commaSpotEnd - commaSpotStart;
    scrubbedD3 = stringStudent.substr(commaSpotStart, commaDist);
    commaSpotStart = commaSpotEnd + 1;
    commaSpotEnd = stringStudent.find(",", commaSpotStart);
    commaDist = commaSpotEnd - commaSpotStart;
    scrubbedDegree = stringStudent.substr(commaSpotStart, commaDist);
    commaSpotStart = commaSpotEnd + 1;
}
void printStringStudent() {
    int i = 0;
    std::cout << scrubbedID << "\tFirst Name: " << scrubbedFName << "\tLast Name: " << scrubbedLName << "\tAge: " << scrubbedAge << "\tdaysInCourse: {";
    std::cout << scrubbedD1 << ", " << scrubbedD2 << ", " << scrubbedD3 << "} Degree Program: " << scrubbedDegree << std::endl;
}
void convertAge() {
    convAge = 0;
    for (int i = 0; i < scrubbedAge.length(); i++) {
        convAge = convAge * 10 + scrubbedAge[i] - '0';
    }
}
void convertD1() {
    convD1 = 0;
    for (int i = 0; i < scrubbedD1.length(); i++) {
        convD1 = convD1 * 10 + scrubbedD1[i] - '0';
    }
}
void convertD2() {
    convD2 = 0;
    for (int i = 0; i < scrubbedD2.length(); i++) {
        convD2 = convD2 * 10 + scrubbedD2[i] - '0';
    }
}
void convertD3() {
    convD3 = 0;
    for (int i = 0; i < scrubbedD3.length(); i++) {
        convD3 = convD3 * 10 + scrubbedD3[i] - '0';
    }
}
void convertDegree() {
    if (scrubbedDegree == "SECURITY") {
        convDegree = SECURITY;
    }
    else if (scrubbedDegree == "NETWORK") {
        convDegree = NETWORK;
    }
    else if (scrubbedDegree == "SOFTWARE") {
        convDegree = SOFTWARE;
    }
    else {
        std::cout << "ERROR\n";
    }
}
void convert() {
    convertAge();
    convertD1();
    convertD2();
    convertD3();
    convertDegree();
}

int main()
{  
   cout << "Course Title: Scripting and Programming - Applications - C867\n";
   cout << "Language Used: C++\nStudent ID: 011142624\nName: Isaiah Bullock\n";
   const string studentData[] = {
 "A1,John,Smith,John1989@gm ail.com,20,30,35,40,SECURITY", "A2,Suzan,Erickson,Erickson_1990@gmailcom,19,50,30,40,NETWORK", "A3,Jack,Napoli,The_lawyer99yahoo.com,19,20,40,33,SOFTWARE", "A4,Erin,Black,[email protected],22,50,58,40,SECURITY", "A5,Isaiah,Bullock,[email protected],21,20,25,30,SOFTWARE"
   };

   Roster classRosterArray(5);
   scrub(studentData[0]);
   convert();
   classRosterArray.add(scrubbedID, scrubbedFName, scrubbedLName, scrubbedEmail, convAge, convD1, convD2, convD3, convDegree);
   scrub(studentData[1]);
   convert();
   classRosterArray.add(scrubbedID, scrubbedFName, scrubbedLName, scrubbedEmail, convAge, convD1, convD2, convD3, convDegree);
   scrub(studentData[2]);
   convert();
   classRosterArray.add(scrubbedID, scrubbedFName, scrubbedLName, scrubbedEmail, convAge, convD1, convD2, convD3, convDegree);
   scrub(studentData[3]);
   convert();
   classRosterArray.add(scrubbedID, scrubbedFName, scrubbedLName, scrubbedEmail, convAge, convD1, convD2, convD3, convDegree);
   scrub(studentData[4]);
   convert();
   classRosterArray.add(scrubbedID, scrubbedFName, scrubbedLName, scrubbedEmail, convAge, convD1, convD2, convD3, convDegree);
   classRosterArray.printAll();

   

   }

学生.cpp

#include <iostream>
#include "degree.h"
#include "student.h"

using std::string;

Student::Student(string iStudentID, string iFName, string iLName, string iEmail, int iAge, int daysToCom1, int daysToCom2, int daysToCom3, DegreeProgram iDegree) {
    setID(iStudentID);
    setFName(iFName);
    setLName(iLName);
    setEmail(iEmail);
    setAge(iAge);
    setComArray(daysToCom1, daysToCom2, daysToCom3);
    setDegree(iDegree);
}

void Student::setID(string iStudentID) {
        studentID = iStudentID;
    }
void Student::setFName(string iFName) {
        fName = iFName;
    }
void Student::setLName(string iLName) {
        lName = iLName;
    }
void Student::setEmail(string iEmail) {
        email = iEmail;
    }
void Student::setAge(int iAge) {
        age = iAge;
    }
void Student::setComArray(int daysToCom1, int daysToCom2, int daysToCom3) {
        numDaysToCom[0] = (daysToCom1);
        numDaysToCom[1] = (daysToCom2);
        numDaysToCom[2] = (daysToCom3);
    }
void Student::setDegree(DegreeProgram iDegree) {
        degree = iDegree;
    }

string Student::getID() {
        return studentID;
    }
string Student::getFName() {
        return fName;
    }
string Student::getLName() {
        return lName;
    }
string Student::getEmail() {
        return email;
    }
int Student::getAge() {
        return age;
    }
int Student::getDay1() {
        return numDaysToCom[0];
    }
int Student::getDay2() {
    return numDaysToCom[1];
}
int Student::getDay3() {
        return numDaysToCom[2];
    }
double Student::getAvgDays() {
        double avg = 0;
        for (int i = 0; i < 3; i++) {
            avg = avg + numDaysToCom[i];
        }
        std::cout << avg << " is the average amount of days in the three courses\n";
        return avg; 
    }
DegreeProgram Student::getDegree() {
        return degree;
    }

void Student::print() {
    int i;
    std::cout << studentID << "\tFirst Name: " << fName << "\tLast Name: " << lName << "\tAge: " << age << "\tdaysInCourse: {";
    for (i = 0; i < 2; i++) {
        std::cout << numDaysToCom[i] << ", ";
    }
    std::cout << numDaysToCom[i] << "} Degree Program: ";
    switch (degree) {
        case 0:
            std::cout << "SECURITY\n";
            break;
        case 1:
            std::cout << "NETWORK\n";
            break;
        case 2:
            std::cout << "SOFTWARE\n";
            break;
        default:
            std::cout << "INVALID DEGREE\n";
    }
}

名册.cpp

#include <iostream>
#include "roster.h"
#include "student.h"
#include "degree.h"

Roster::Roster() {
    capacity = 0;
    size = 0;
    Student classRosterArray[1];
}

Roster::Roster(int capacity) {
    capacity = capacity;
    size = 0;
    Student* classRosterArray = new Student[capacity];
}

/*
Roster::Roster(int capacity) {
    this->capacity = capacity;
    this->size = 0;
    this->classRosterArray = new Student * [capacity];
}
*/
Roster::~Roster() {
    for (int i = 0; i = size; i++) {
        delete this->classRosterArray[i];
    }
    delete classRosterArray;
}

void Roster::add(string iStudentID, string iFName, string iLName, string iEmail, int iAge, int daysToCom1, int daysToCom2, int daysToCom3, DegreeProgram iDegree) {
    classRosterArray[size] = new Student(iStudentID, iFName, iLName, iEmail, iAge, daysToCom1, daysToCom2, daysToCom3, iDegree);
    size += 1;
}

void Roster::remove(string studentID) {
    for (int i = 0; i < size; i++) {
        if (classRosterArray[i]->getID() == studentID) {
            delete classRosterArray[i];
        }
        else {
            std::cout << "No student with ID\n";
        }
    }
}

void Roster::printAll() {
    for (int i = 0; i < size; i++) {
        (this->classRosterArray)[i]->print();
    }
}

void Roster::printAverageDaysInCourse(string studentID) {
    for (int i = 0; i < size; i++) {
        if (classRosterArray[i]->getID() == studentID) {
            classRosterArray[i]->getAvgDays();
        }
        else {
            std::cout << "No student with ID\n";
        }
    }
}

void Roster::printInvalidEmails() {
    for (int i = 0; i < size; i++) {
        classRosterArray[i]->getEmail();
    }
}

如果有帮助的话我可以包含我的标题，但我真的不认为这会改变任何事情。

我尝试输入其他人的代码，但没有成功。我还尝试将默认构造函数更改为大小为 1，只是为了看看是否允许至少一项内容进入，但这也不起作用。

Answer 1

好吧，关于类和构造函数如何工作的一些严重误解

Roster::Roster() {
    capacity = 0;
    size = 0;
    Student classRosterArray[1];
}

Roster::Roster(int cap) {
    capacity = cap;
    size = 0;
    Student* classRosterArray = new Student[capacity];
}

应该是

Roster::Roster() {
    capacity = 0;
    size = 0;
    array = nullptr;
}

Roster::Roster(int capacity) {
    capacity = capacity;
    size = 0;
    array = new Student[capacity];
}

有一个类似这样的类

class Roster
{
public:
    Roster();
    Roster(int capacity);
    ...
private:
    int capacity;
    int size;
    Student* array;
};