how to pass class objects to another class member arrays in C++

Question

I am now solving a class declare problem in C++. I create a class phoneRec to store the information of name and phone number, and another class phoneBk, which has 3 member arrays to store the class phoneRec objects that carried name and number information. I declared functions in phoneRec to input and save name and phone number, but I don't know how to declare functions in phoneBk to check and delete the information that from the phoneRec objects.

here is the code that I write, is there any ideas for me to complete the task?

#define _CRT_SECURE_NO_WARNINGS 1
#include <iostream>
using namespace std;
#include <string.h>
class phoneRec
{
public:

    void setName(char NM[]);
    char *getName();
    
    void setNumber(int num);
    int getNumber();


private:
    int numb;
    char name[80];
    

};

void phoneRec::setName(char NM[])
{
    strncpy(name, NM, 79);
}

char *phoneRec::getName()
{
    return name;
}


void phoneRec::setNumber(int num)
{
    numb=num;
}
int phoneRec::getNumber()
{
    return numb;
}



class phoneBk
{
public:

    void deletemem();
    void group();
    phoneRec *obj;

};

void phoneBk::deletemem() 
{ 
    ;
}

void phoneBk::group()
{
    phoneBk Family[1000];

    phoneBk Friend[1000];

    phoneBk Junk[1000];

}

char name[80]; is this a requirement over using std::string? Are you permitted to use std::vector? — drescherjm
– drescherjm, Commented Nov 28, 2020 at 16:28
I think phoneBk Family[1000]; should not be an array. A family will not have 1000 phone books. A phone book may have 1000 entries. — drescherjm
– drescherjm, Commented Nov 28, 2020 at 16:30
I can only use array to represent the strings in this task：（ — Evelyn
– Evelyn, Commented Nov 28, 2020 at 16:31
I assume phoneRec *obj; you want to declare a dynamic array of phoneRec objects in a phoneBk. — drescherjm
– drescherjm, Commented Nov 28, 2020 at 16:32
the phonebook is to store the contact information, such as I have a name and phone number, after input these data, then I let to store in a array called Family, which can be regard as a category that govern the contact person — Evelyn
– Evelyn, Commented Nov 28, 2020 at 16:34

ytlu · Accepted Answer · 2020-11-28 19:35:34Z

I make a suggested method by adding some flags in the phoneRec to mark for group and delet status. A deleted record is marked as Deleted. But it is not removed until you issue a flush() command. That is very typical way. Because actually remove elements from an array require reallocate and re-arrange the whole array. It shall not be done very frequently.

The class phoneRec

enum GROUP {Family=0, Friend=1, Junk=2};
enum STATUS {Active=0, Deleted=1};
class phoneRec
{
public:
    phoneRec(): group(Junk), deleted(Active){;}
    phoneRec(const int n, const char *a): numb(n), group(Junk), deleted(Active)
    {
        memcpy(this->name, a, 79);
    }
    phoneRec(const int n, const char *a, int g): numb(n), group(g), deleted(Active)
    {
       memcpy(this->name, a, 79);
    }
    void setName(const char NM[]);
    const char *getName() const;

    void setNumber(const int num);
    int getNumber() const;

    void setGroup(const int g) {group = g;}
    void print() const
    {
        std::cout << this->name;
        std::cout << "  No = " << this->numb;
        std::cout << " group = " << this->group << std::endl;
    }
    int status() const { return this->deleted;}
    void del() { this->deleted = Deleted;}
private:
    int numb;
    char name[80];
    int group;
    int deleted;
};

I change strncpy to memcopy (easier to use). And the class PhoneBK keep an array of PhoneRec(MaxRec).

class phoneBk
{
 public:
    phoneBK() = delete;
    phoneBk(const int nx): MaxRec(nx), curNum(0), nDel(0)
    {
       p_rec = new phoneRec [MaxRec];
    }
   ~phoneBk() { delete [] p_rec ;}
    phoneRec operator[](const int i) const {return p_rec[i];}
    phoneRec& operator[](const int i) {return p_rec[i];}
    int n() const {return this->curNum;} // return current record
    int AddNewRec(const int nu, const char *nm)
     {
       if (curNum >= MaxRec) return 0;
       p_rec[curNum] = phoneRec(nu, nm, Junk);
       ++curNum;
       return 1;
      }
    int AddNewRec(const int nu, const char *nm, const GROUP g)
     {
        if (curNum >= MaxRec) return 0;
        p_rec[curNum] = phoneRec(nu, nm, g);
        ++curNum;
        return 1;
     }
    void deleteRec() // mark the current record deleted
      {
         p_rec[curNum].del();
         ++nDel;
      }
    void deleteRec(const int i) // mark ith record deleted
      {
        p_rec[i].del();
        ++nDel;
      }
    void flush()  // refresh array removing deleted
      {
         phoneRec *tmp = new phoneRec [MaxRec];
         int nc = 0;
         for (int i=0; i<curNum; i++)
         {
            if (p_rec[i].status() == Deleted) continue;
            memcpy((void*)(tmp+nc), (void*)(p_rec+i), sizeof(phoneRec) );
            ++nc;
         }
         delete []  this->p_rec;
         this->p_rec = tmp;
         tmp = nullptr;
         this->curNum -= nDel;
         this->nDel = 0;
       }
     private:
        phoneRec *p_rec; // phone array.
        int curNum;   // current enroll number.
        const int MaxRec; // Max records allow.
        int nDel;      // total number marked deleted.
     };

And finally, a test main()

#include <iostream>
#include <string.h>
using namespace std;
int main()
{
   phoneBk fon(10);
   fon.AddNewRec(12345, "aaaa", Friend);
   fon.AddNewRec(22222, "bbbb", Friend);
   fon.AddNewRec(33333, "cccc", Friend);
   fon.AddNewRec(44444, "dddd", Family);
   fon.AddNewRec(55555, "ffff", Family);
   fon.AddNewRec(66666, "gggg", Family);
   fon.AddNewRec(12345, "aaaa", Junk);
   fon.AddNewRec(12345, "aaaa", Junk);
   std::cout << "Current number = "<< fon.n() << std::endl;
   for (int i=0; i<fon.n(); i++) fon[i].print();
   fon.deleteRec(); // del current rec
   fon.deleteRec(3); // del 4th rec
   fon.flush(); //fresh array
   std::cout << "Current number = "<< fon.n() << std::endl;
   for (int i=0; i<fon.n(); i++) fon[i].print();
   return 0;
}

The result:

$ ./a.exe
Current number = 8
aaaa  No = 12345 group = 1
bbbb  No = 22222 group = 1
cccc  No = 33333 group = 1
dddd  No = 44444 group = 0
ffff  No = 55555 group = 0
gggg  No = 66666 group = 0
aaaa  No = 12345 group = 2
aaaa  No = 12345 group = 2

Current number = 6
aaaa  No = 12345 group = 1
bbbb  No = 22222 group = 1
cccc  No = 33333 group = 1
ffff  No = 55555 group = 0
gggg  No = 66666 group = 0
aaaa  No = 12345 group = 2

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