c++ using functions from another class

Question

I'm still very new to programming, and have bumped into an issue that I'm sure is very basic.

So what I'm trying to do, is use functions that I defined in one .h-file, and then wrote out in the .cpp-file belonging to that .h-file, in another .cpp-file. Is this possible?

Date.h file:

#pragma once

#ifndef DATE_GUARD
#define DATE_GUARD

#include <iostream>

class Date
{
public:
    Date();
    Date(int);
    int getDay();
    int getMonth();
    int getYear();
    int getDate();
    bool leapYear();
    ~Date();
private:
    int theDate;
};

#endif

CPR.h file

#pragma once
#include"Date.h"

class CPR
{
public:
    CPR();
    CPR(unsigned long); //DDMMYYXXXX
    Date getDate();
    int getFinalFour();
    bool validate();
    int getFirstCipher();
    int getSecondCipher();
    int getThirdCipher();
    int getFourthCipher();
    int getFifthCipher();
    int getSixthCipher();
    int getSeventhCipher();
    int getEighthCipher();
    int getNinthCipher();
    int getTenthCipher();
    ~CPR();

private:
    int CPRNummer;
    Date birthday;
};

Date.cpp file

#include "Date.h"

Date::Date()
{
}

Date::Date(int aDate)
{
    theDate = aDate;
}

int Date::getDay()
{
    return theDate / 10000;
}

int Date::getMonth()
{
    return (theDate / 100) % 100;
}

int Date::getYear()
{
    return (theDate % 100);
}

bool Date::leapYear()
{
    if (getYear() % 4 != 0)
        return false;
    if (getYear() % 100 == 0 && getYear() % 400 != 0)
        return false;
    return true;
}

int Date::getDate()
{
    return theDate;
}

Date::~Date()
{
}

CPR.cpp file (only important part)

#include "CPR.h"
#include "Date.h"
#include <iostream>

bool CPR::validate()
{
    if (getDay() < 1 || getDay() > 31)
        return false;

    if (getMonth() < 1 || getMonth() > 12)
        return false;

    if (getYear() < 1700 || getYear() > 2100)
        return false;

    if (getMonth() == 2 && leapYear() && getDay() > 29)
        return false;

    if (!leapYear() && getMonth() == 2 && getDay() > 28 || getMonth() == 4 && getDay() > 30 || getMonth() == 6 && getDay() > 30 || getMonth() == 9 && getDay() > 30 || getMonth() == 11 && getDay() > 30)
        return false;
    return true;
}

So I'm trying to use the leapYear(), getMonth(), getDay() and getYear() functions from Date.cpp in CPR.cpp.

You have to specify the object you want to call the member function on. Like e.g. `birthday.getDay()`. Just about any beginners book or tutorial should have shown you that. And if the tutorials or books you read haven't shown you that, then stop using them and [get some good books instead](https://stackoverflow.com/a/388282/440558). — Some programmer dude, Feb 27 '18 at 07:59
@Someprogrammerdude thx. Your answer helped! Even though a bit rude, it helped. — T. Aalbaek, Feb 27 '18 at 08:10
Rather handle each month in a separate `if` I would write `int limit; switch(birthday.getMonth()) { case 9: case 4: case 6: case 11: limit = 30; break; case 1: case 3: case 5: case 7: case 8: case 12: limit = 31; break; case 2: limit = birthday.leapYear() ? 29 : 28; default: limit = 0; break; }` and then test if outside `[1..limit]` — Martin Bonner supports Monica, Feb 27 '18 at 10:06
and the odd sequence 9, 4, 6, 11 is from "30 days hath September, April, June and November..." — Martin Bonner supports Monica, Feb 27 '18 at 10:07

score 0 · Answer 1 · answered Feb 27 '18 at 08:00

0

In CPR.cpp, you need to

#include "Date.h"

and then, within CPR.cpp, you can create an object of type Date and use its members.

answered Feb 27 '18 at 08:00

Demosthenes

1,515
10
22

-1: You are technically correct, but deeply misleading. `class CPR` has a member function `getDate()` and a member variable `birthday`, as such the OP is almost *certainly* trying to call `birthday.getDay();`. Thjere is also no need to `#include "Date.h"` in `CPR.cpp` because it is included in `CPR.h`. – Martin Bonner supports Monica Feb 27 '18 at 08:06
@MartinBonner you are absolutely correct. I called birthday.getDay(); and so on, and it worked. Simple mistake with a simple fix. – T. Aalbaek Feb 27 '18 at 09:47

score 0 · Accepted Answer · answered Feb 27 '18 at 08:11

Try this. But your program seems still incorrect:

bool CPR::validate()
{
    if (birthday.getDay() < 1 || birthday.getDay() > 31)
        return false;

    if (birthday.getMonth() < 1 || birthday.getMonth() > 12)
        return false;

    if (birthday.getYear() < 1700 || birthday.getYear() > 2100)
        return false;

    if (birthday.getMonth() == 2 && birthday.leapYear() && birthday.getDay() > 29)
        return false;

    if (!birthday.leapYear() && birthday.getMonth() == 2 && birthday.getDay() > 28 || birthday.getMonth() == 4 && birthday.getDay() > 30 || birthday.getMonth() == 6 && birthday.getDay() > 30 || birthday.getMonth() == 9 && birthday.getDay() > 30 || birthday.getMonth() == 11 && birthday.getDay() > 30)
        return false;
    return true;
}

c++ using functions from another class

2 Answers2