How do I pass objects through different classes properly?

Question

So for my task, I have 3 classes, Student, Date, and Address. Student class has two instances of the Date class and one of the Address class.

My goal is to be able to from the main.cpp create an array of objects from the Student class. I have tried a few different ways but I run into various problems.

edit: This has been marked as a duplicate but all of the other questions I find don't fully/sufficiently answer my question for what I am trying to do here, please link me to a question that does as I cannot find it. I am trying to create an object from class Student that also has objects from classes date and address.

Here is my code now in relevant files.

student.cpp

#include "student.h"


using namespace std;

Student::Student(){
Student::fName = "";
Student::lName = "";
Student::gpa = "";
Student::credits = "";
Student::address;
Student::dBirth;
Student::dGraduation;



}//end Default Constructor

Student::Student(string firstName, string lastName, string s_gpa, string s_credits, Date *s_dBirth, Date *s_dGraduation, Address *s_address){
Student::fName = firstName;
Student::lName = lastName;
Student::gpa = s_gpa;
Student::credits = s_credits;
Student::dBirth = s_dBirth;
Student::dGraduation = s_dGraduation;
Student::address = s_address;


}//end Constructor

student.h

#ifndef STUDENT_H
#define STUDENT_H

#include <string> 
#include <iostream>
#include "date.h"
#include "address.h"

class Student{
private:
    std::string fName;
    std::string lName;
    std::string gpa;
    std::string credits;
    Date *dBirth;
    Date *dGraduation;
    Address *address;

public:
    Student();//Default constructor
    Student(std::string fName, std::string lName, std::string gpa, std::string credits, Date *dBirth, Date *dGraduation, Address *address);//Constructor
    ~Student();//Destructor


};//end Student Class


#endif // STUDENT_H

date.cpp

#include "date.h"

using namespace std;

Date::Date(){
Date::month = 0;
Date::day = 0;
Date::year = 0;
}//End default constructor

Date::Date(int sMonth, int sDay, int sYear){
Date::month = sMonth;
Date::day = sDay;
Date::year = sYear;

}//End constructor

date.h

#ifndef DATE_H
#define DATE_H

#include <string>
#include <iostream>


class Date{
private:
    int month;
    int day;
    int year;
public:
    Date();
    Date(int month, int day, int year);
    std::string getDate();
};//end Date Class

#endif // DATE_H

address.cpp

#include "address.h"

using namespace std;

Address::Address(){
Address::aLine1 = "";
Address::aLine1 = "";
Address::city = "";
Address::state = "";
Address:zip = "";
}//end Default Constructor

Address::Address(string line1, string line2, string sCity, string sState, string sZip){
Address::aLine1 = line1;
Address::aLine2 = line2;
Address::city = sCity;
Address::state = sState;
Address::zip = sZip;

}//End Constructor

address.h

#ifndef ADDRESS_H
#define ADDRESS_H

#include <string>
#include <iostream>


class Address{
private:
    std::string aLine1;
    std::string aLine2;
    std::string city;
    std::string state;
    std::string zip;
public:
    Address();
    Address(std::string aLine1, std::string aLine2, std::string city, std::string state, std::string zip);
    std::string getAddress();
};

#endif // ADDRESS_H

I am fairly new to C++, any and all help is greatly appreciated.

Answer 1

First of all add your main() so that we can see what goes wrong. Second - I presume you have a problem with the pointer part. See the documentation on the new operator in C++ (also check the delete operator).

Basically you have two easy to use ways of passing object:

• You can dynamically allocate the object using the new operator and pass the pointer to your Student - this has the disadvantage that you have to manually deallocate the memory for the dynamically allocated object (using delete or delete[] in case of an array)
• Create objects on the stack - this has the advantage that you need not concern yourself with the memory management.

Example (using new):

Date* d1 = new Date(...);
Date* d2 = new Date(...);
Address* a = new Address(...);
Student* s = new Student(..., d1, d2, a);

...

delete d1;
d1 = NULL;
delete d2;
d2 = NULL;
delete a;
a = NULL;
delete s;
s = NULL;

If you want to do that you can also add the delete-s in the destructor of your Student class:

Student::~Student()
{
  delete dBirth;
  dBirth = NULL;
  delete dGraduation;
  dGraduation = NULL;
  delete address;
  address = NULL;
}

Note that you still have to dispose of Student* s using delete.

Example (using stack):

Date d1(...);
Date d2(...);
Address a(...);
Student s(..., &d1, &d2, &a); // the & operator tells the compiler: pass these objects by reference

You can also make a combination of those two ways I have described above. Also your code is somewhat weird as I have mentioned in the comments:

1. No need of mentioning the various scopes so many times - once you say

   string Address::getAddress() {
     ...
   }
   

   you don't need to explicitly mention the scope of all members you use in its body unless they have a different namespace

2. Add access to the members of your classes - you have done this (partially) for your Address and Date classes but right now you have NO WAY of accessing Student's members since they are all private! Add get() and/or set(...) methods whenever you see it adequate.

3. I see your getAddress() and getDate() are empty. I presume you don't know how to implement those. Here is a possible implementation:

   std::string Address::getAddress()
   {
     return aLine1 + " | " + aLine2 + " | " + ... + zip; # + stands for concatenation
   }
   
   # requires #include<sstream>
   std::string Date::getDate()
   {
     std::stringstream ss;
     ss << year << "/" << month << "/" << day;
   
     return ss.str();
   }
   

4. Use this instead of adding the class scope in front of the variable (example below is for the constructor of Address class):

   Address(std::string aLine1, ...)
   {
     this->aLine1 = aLine1;
     ...
   }
   

   Or simply call the method's parameter in a different way to avoid name conflicts. The good old-fashioned way is to add "_" in front of the name:

   Address(std::string _aLine1, ...)
   {
     aLine1 = _aLine1;
     ...
   }
   

EDIT:

Here is how your headers and sources should be connected:

1. student.h - include in student.cpp (because student.cpp implements the content you have described in your student.h) and main.cpp (because you want to declare one or more Student objects and do something with those; since student.h includes address.h and date.h when you include student.h in your main.cpp the code there will "see" what's in those headers too)
2. address.h - include in address.cpp (because address.cpp implements the content you have described in your address.h), student.h (because you have declared that your Student class has one class member of class Address) and main.cpp (because you want to declare one or more Address objects and pass those to a bunch of Student objects)
3. date.h - include in date.cpp, student.h (because date.cpp implements the content you have described in your date.h) and main.cpp (because you want to declare one or more Date objects and pass those to a bunch of Student objects)

So basically here's a short list of the includes for each of the files (I'm excluding the and all the rest):

• student.h : address.h, date.h
• student.cpp : student.h
• address.cpp : address.h
• date.cpp : date.h
• main.cpp : student.h

EDIT: Additional clarification: date.h and address.h are included in student.h, which accordingly is added to the main.cpp. This creates a chain of headers (address.h and date.h are indirectly included in the main.cpp through the student.h) and that is why I have omitted those in the final list.