Date Class C++

[o1q592yv]

Hi guys! currently making a Date Class and as I am compiling in g++ I am getting the following errors when I compute my Datemain.cpp file:

[rrazzak@cloudland ~]$ g++ -g -Wall -o ExecutableFileName Datemain.cpp
/tmp/cc4wbMX0.o: In function `main':
/home/rrazzak/Datemain.cpp:7: undefined reference to `Date::Date()'
/home/rrazzak/Datemain.cpp:8: undefined reference to `Date::increment()'
/home/rrazzak/Datemain.cpp:10: undefined reference to `Date::display1()'
/home/rrazzak/Datemain.cpp:11: undefined reference to `Date::increment()'
/home/rrazzak/Datemain.cpp:14: undefined reference to `Date::display2()'
/home/rrazzak/Datemain.cpp:15: undefined reference to `Date::increment()'
/home/rrazzak/Datemain.cpp:18: undefined reference to `Date::Date(int, int, int)'
/home/rrazzak/Datemain.cpp:19: undefined reference to `Date::increment()'
/home/rrazzak/Datemain.cpp:20: undefined reference to `Date::display1()'
/home/rrazzak/Datemain.cpp:23: undefined reference to `Date::increment()'
/home/rrazzak/Datemain.cpp:24: undefined reference to `Date::display2()'
collect2: ld returned 1 exit status

Yet when ever I do this: g++ -g -Wall -o ExecutableFileName Datemain.cpp Date.cpp, i am able to compile.. I assume you do not include the cpp file in main because you already include the header file, but I don't quite understand the undefined reference error I am getting

Date.cpp file:

#include "Date.h" //includes the Date header file
#include <iostream>
#include <cassert> //lets us use assertions in C ++

using namespace std;

//default constructor with default values
Date::Date()
{
    month = 1;//default month value
    day = 1;//default day value
    year = 2000;//default year value
}
//postcondition: a Date with a month, day and year has been created

//precondition: Date will check if any of the conditions have been violated
              
Date::Date(int Month,int Day,int Year)
{
    if((Month < 1||Month > 12)||(Day < 1||Day > 31)||(Year < 1900||Year > 2020))
    {
        std::cout<<"Invalid"<<std::endl;

    }
    else
    {
        month = Month;
        day = Day;
        year = Year;
    }
}
//postcondition: Date checked that the code does not violate any of the parameters

//precondition: Day will have been incremented by 1
void Date::increment()
{
    //month += 1;
    //assert(month >= 1 && month <= 12);
    day += 1;
    assert(day >= 1 && day <= 31);
    if(month == 2 && day == 28 || day == 29)
    {
      if(year % 4 || year % 400)
       {
	 std::cout<<"Thats a Leap Year"<<std::endl;
	 //month += 1;
	 day += 1 ;
	 //year++;
	 assert(day >= 1 && day <= 31);
	 assert(month >= 1 && month <= 12);
       }
     }
    
}
//postcondition: Day has been incremented by 1

void Date::display1()
{
    std::cout<<month<<'/'<<day<<'/'<<year<<std::endl;
}
//postcondition: Date has been displayed in number format

void Date::display2()
{
    string Month;
    switch(month)
    {
        case 1:
            Month="January";
            break;

        case 2:
            Month="February";
            break;

        case 3:
            Month="March";
            break;

        case 4:
            Month="April";
            break;

        case 5:
            Month="May";
            break;

        case 6:
            Month="June";
            break;

        case 7:
            Month="July";
            break;

        case 8:
            Month="August";
            break;

        case 9:
            Month="September";
            break;

        case 10:
            Month="October";
            break;

        case 11:
            Month="November";
            break;

        case 12:
            Month="December";
            break;
    }

    std::cout<<Month<<'/'<<day<<'/'<<year<<std::endl;
}
//postcondition: Date is displayed in word format 

Date.h:

#ifndef DATE_H
#define DATE_H
class Date
{
private:
    int month;
    int day;
    int year;

public:
    Date();
    Date(int month,int day,int year);
    void display1();
    void display2();
    void increment();
};
#endif //DATE_DATE 

Datemain.cpp:

#include <iostream>
#include "Date.h" //includes Date header file
#include <string>
using namespace std;
int main()
{
    Date d;
    d.increment();

    d.display1();
    d.increment();
    std::cout<<std::endl;

    d.display2();
    d.increment();
    std::cout<<'\n'<<std::endl;

    Date today(1,29,2017);
    today.increment();
    today.display1();
    std::cout<<std::endl;

    today.increment();
    today.display2();
    std::cout<<"\n\n"<<std::endl;
    std::cout<<"ALL TESTS PASSED! YAAY!"<<std::endl;
    return 0;
}

[Peter87]

Undefined reference just means the linker can't find a definition of whatever it is complaining about. You need to pass Date.cpp to g++ otherwise it will not compile and link the content of that file.

[o1q592yv]

How would I do that?? because my first thought was to include the Date.cpp in my main.

[Peter87]

Do it as you did.

g++ -g -Wall -o ExecutableFileName Datemain.cpp Date.cpp

[o1q592yv]

it worked O.o

[rrazzak@cloudland ~]$ g++ -g -Wall -o ExecutableFileName Datemain.cpp Date.cpp
[rrazzak@cloudland ~]$

So I assume when I do that, it compiles both files?

[Peter87]

Yes.

[TheIdeasMan]

@thenomster

You should always compile with -Wextra -pedantic-errors as well. There are quite of number of very handy warning options not enable by -Wall.

Here are even more still not enabled by the above options:

http://www.cplusplus.com/forum/general/183731/#msg899203

If you don't have a recent version of g++, then specify a std as well -std=c++14 version 6.0 or later of g++ defaults to c++14. c++17 is out soon, both g++ and clang++ have already implemented quite a bit of it.

Good Luck !!