c++ Help

[Jay Nguyen]

I need to create a DOB out of OCCCDate in the person header file and then call it in the testOCCCDate.cpp. but i dont know how please help me..

 

here is my UML;

Person

#firstname: String

#lastName:String

DOB :OCCCDate/// i having problem creating this DOB... some1 help me please

OCCCDate.zip

[Andre S. Veteran]

What is a DOB and an OCCCDate? What's the context? What's the problem? Put some work in your question so others don't have to do that work to figure out what you mean.

[Jay Nguyen]

DOB is Date Of Birth. OCCCDate is a Header file that i created.

[+Majesticmerc MVC]

From what I understand, you want to add a  date of birth into the Person class.

 

Step 1

To begin, you'll need to add a date of birth field into the person class. You'll need to do this in two parts.

 

First, you need to include the OCCCDate class header file inside your Person.h header file...

 

Person.h
---------------------------------------------------------

//Person.h

#ifndef PERSON_H
#define PERSON_H
#include<string>

// Add the OCCCDate.h header file...
#include "OCCCDate.h"

...

Once you've added the header file, you can create a private class member inside your person class like you've described in your original post.

 

Person.h
---------------------------------------------------------

...

class Person{
    private:
        string firstname;
        string lastname;

        // Add an OCCCDate class here as a member, just like you did for the strings above.

    public:

...    

Step 2:

It's unlikely that you'll want a person to have the current system date as their date of birth, so you'll need to add a parameter to the Person constructor to pass a date of birth. like this:

Person.h
---------------------------------------------------------

...

class Person{

    private:
        ...

    public:
        Person(string firstName, string lastName, OCCCDate dateOfBirth);
//                                                ^--------,---------^
//                                                         New parameter in the constructor.

...    

Don't forget you'll need to copy the date of birth parameter in the constructor in your Person.cpp file too! Looking at your .cpp file, you're almost there already :)).

Once you've done that, you can add a method to the Person class to retrieve the date of birth (just like Person::getFirstName() and Person::getLastName()), and you're good to go!

Hope this helps :)

[Jay Nguyen]

When i I use #include "OCCCDate.h" in the person file it gave me more error.

OCCCDate.zip

[Jay Nguyen]

bump?

[+Majesticmerc MVC]

I assume you're seeing an error talking about "redefinition of class OCCCDate"? That's because of the following lines in OCCCDate.h...

 

//file OcccDate.h

#ifndef OCCCDATE_H
#define OCCCDDATE_H

See the spelling mistake in the #define line (hint: two 'D's in DDATE)? You'll need to fix that like this...

 

//file OcccDate.h

#ifndef OCCCDATE_H
#define OCCCDATE_H

Once you fix that, it should work. Because of the spelling mistake, the #ifndef block was always TRUE (because OCCCDATE_H was never defined), and the compiler tried to define the class again, which is bad ;).

[Andre S. Veteran]

Or you could just use #pragma once rather than #ifndef #define #endif. All major compilers (MSVC, GCC, Clang, Intel, etc.) support it and it reduces the potential for bugs. Like the one you just had.

[Jay Nguyen]

WOW just that small mistake and it took me 3 days. jesus. programming is so hard.

[+Majesticmerc MVC]

Or you could just use #pragma once rather than #ifndef #define #endif. All major compilers (MSVC, GCC, Clang, Intel, etc.) support it and it reduces the potential for bugs. Like the one you just had.

While I agree with you in practice, if it's an assignment it may be that the tutor is sticking strictly to the standard, and using #pragma vs a standard-compliant alternative may lose the student points.

WOW just that small mistake and it took me 3 days. jesus. programming is so hard.

Indeed it is, but its also incredibly gratifying if you enjoy it. Glad your issue is sorted. :)

[Andre S. Veteran]

WOW just that small mistake and it took me 3 days. jesus. programming is so hard.

No, C++ is just ****. No decent programming language uses header files and silly macro tricks just to get programs to compile. Don't let your opinion of programming be tainted by the arcane and irrelevant rules of C++, even though it happens that this is what your teacher misleadingly thought would be a good idea to show you first. If your teacher thinks C++ is good just ask him "why are there header files in C++?" and watch him be embarassed. I fondly remember being unable to receive an intelligent answer to this question in my first programming class.

 

It ****es me off to think many people must quit programming simply because they're being shown the most bizarre and capricious language in existence first, and assume that all programming must be like that. It's not.

 

Arm yourself with courage and a good C++ book (I used The C++ Primer Plus by Stephen Prata), and when you're through with this course, take a look at such beautiful languages as Python, C#, F#, Scala, Rust, etc. I guarantee your outlook on programming will change for the better and dramatically so.

[FloatingFatMan]

No, C++ is just ****. No decent programming language uses header files and silly macro tricks just to get programs to compile. Don't let your opinion of programming be tainted by the arcane and irrelevant rules of C++, even though it happens that this is what your teacher misleadingly thought would be a good idea to show you first. If your teacher thinks C++ is good just ask him "why are there header files in C++?" and watch him be embarassed. I fondly remember being unable to receive an intelligent answer to this question in my first programming class.

 

It ****es me off to think many people must quit programming simply because they're being shown the most bizarre and capricious language in existence first, and assume that all programming must be like that. It's not.

 

 

That said, he didn't exactly help himself with that function name. VERY easy to mistype that, so I'm not at all surprised he didn't spot it...

[Andre S. Veteran]

That said, he didn't exactly help himself with that function name. VERY easy to mistype that, so I'm not at all surprised he didn't spot it...

At least when you mistype something in most programming languages, you tend to get something from the compiler like "hey what's that you typed in file (Z) at line (X) column ( Y), I have no idea what that is." In C++ you tend to get the equivalent of "AAAAAAaaaaarglgl.... guh." Much of the difficulty consists of learning how to map the gibberish to actual errors.

[FloatingFatMan]

At least when you mistype something in most programming languages, you tend to get something from the compiler like "hey what's that you typed in file (Z) at line (X) column ( Y), I have no idea what that is." In C++ you tend to get the equivalent of "AAAAAAaaaaarglgl.... guh." Much of the difficulty consists of learning how to map the gibberish to actual errors.

 

Pretty much why I walked away from C/C++ 2 decades ago. :p  Sure it's handy, but it's a pain in the backside, too!

[ILikeTobacco]

WOW just that small mistake and it took me 3 days. jesus. programming is so hard.

It isn't hard. Just tedious and annoying lol. It's always the little things that mess you up in programming.

[ILikeTobacco]

Pretty much why I walked away from C/C++ 2 decades ago. :p  Sure it's handy, but it's a pain in the backside, too!

Same. Gave up on C++ a long time ago. C# all the way. :P

[Karl L.]

At least when you mistype something in most programming languages, you tend to get something from the compiler like "hey what's that you typed in file (Z) at line (X) column ( Y), I have no idea what that is." In C++ you tend to get the equivalent of "AAAAAAaaaaarglgl.... guh." Much of the difficulty consists of learning how to map the gibberish to actual errors.

 

That is why I use Clang for my C and C++ work when possible: its error messages are so much more sane than GCC. In my opinion one of the biggest advantages of Visual Studio's C++ compiler over GCC is its error messages. That said, I think that Clang beats them both by a long shot with exceptionally helpful diagnostic messages. I was going to try to demonstrate Clang's superiority in this regard using the author's code, but it didn't actually make that much of a difference. For the record, the results are as follows:

$ make CXX=g++
g++ -c -std=c++11 -w -O3   Person.cpp -o Person.o
g++ -c -std=c++11 -w -O3   OCCCDate.cpp -o OCCCDate.o
g++ -c -std=c++11 -w -O3   TestOCCCDate.cpp -o TestOCCCDate.o
In file included from Person.h:7:0,
                 from TestOCCCDate.cpp:4:
OCCCDate.h:8:7: error: redefinition of ?class OCCCDate?
In file included from TestOCCCDate.cpp:3:0:
OCCCDate.h:8:7: error: previous definition of ?class OCCCDate?
make: *** [TestOCCCDate.o] Error 1

$ make CXX=clang++
clang++ -c -std=c++11 -w -O3   Person.cpp -o Person.o
clang++ -c -std=c++11 -w -O3   OCCCDate.cpp -o OCCCDate.o
clang++ -c -std=c++11 -w -O3   TestOCCCDate.cpp -o TestOCCCDate.o
In file included from TestOCCCDate.cpp:4:
In file included from ./Person.h:7:
./OCCCDate.h:8:7: error: redefinition of 'OCCCDate'
class OCCCDate{
      ^
./OCCCDate.h:8:7: note: previous definition is here
class OCCCDate{
      ^
In file included from TestOCCCDate.cpp:4:
In file included from ./Person.h:7:
./OCCCDate.h:15:12: error: expected member name or ';' after declaration specifiers
                OCCCDate();//default constructor, uses current system date and time
                ~~~~~~~~ ^
./OCCCDate.h:16:12: error: expected member name or ';' after declaration specifiers
                OCCCDate(int day, int month, int year);//as define above
                ~~~~~~~~ ^
./OCCCDate.h:16:12: error: expected ')'
./OCCCDate.h:16:11: note: to match this '('
                OCCCDate(int day, int month, int year);//as define above
                        ^
4 errors generated.
make: *** [TestOCCCDate.o] Error 1

$ g++ --version
g++ (Debian 4.7.2-5) 4.7.2
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ clang++ --version
Debian clang version 3.0-6.2 (tags/RELEASE_30/final) (based on LLVM 3.0)
Target: x86_64-pc-linux-gnu
Thread model: posix

I can understand why Majesticmerc was able to spot the error whereas nether Clang nor GCC could catch it automatically. Therefore I have to agree with you to some extent. While some compilers do a much better job at printing helpful diagnostic messages than others, it is generally much more difficult to pinpoint errors in C++ than in newer languages like Python. I can generally interpret error messages and pinpoint the mistake in my C++ source code pretty quickly, but I think most of that comes down to experience. I remember Googling basically every error message when I started learning C++ hoping to find the resolution posted somewhere on the Internet. So while I would like to disagree with your assessment, I don't think I realistically can. Therefore I would merely like to point out that Clang prints much better diagnostic messages than other compilers - in most cases.

[fatbeerguy]

No, C++ is just ****. No decent programming language uses header files and silly macro tricks just to get programs to compile. Don't let your opinion of programming be tainted by the arcane and irrelevant rules of C++, even though it happens that this is what your teacher misleadingly thought would be a good idea to show you first. If your teacher thinks C++ is good just ask him "why are there header files in C++?" and watch him be embarassed. I fondly remember being unable to receive an intelligent answer to this question in my first programming class.

 

It ****es me off to think many people must quit programming simply because they're being shown the most bizarre and capricious language in existence first, and assume that all programming must be like that. It's not.

 

Arm yourself with courage and a good C++ book (I used The C++ Primer Plus by Stephen Prata), and when you're through with this course, take a look at such beautiful languages as Python, C#, F#, Scala, Rust, etc. I guarantee your outlook on programming will change for the better and dramatically so.

 

Seems a bit one sided :).

 

1. If you don't want "silly macro tricks" aka include guards then just never include the header more than once, or use #pragma once ;)

2. Header files are used to define the interface/contract. If you have a header which contains int get_magic_for_this_machine(); then you  call that function, it does some magic, you don't need to know about the 9000 other internal functions and classes it may have/use in its cpp file. Any code in a header file is inlined too. Also its possible to write something that only uses headers... but you'll have to endure huge build times.

3. For his problem there is no way the compiler could help him...

 

#ifdef A

#define B // Was this supposed to be A? or is B correct? What about the stuff below? It could mean anything so this could never be statically checked at build time

#define C

#define D

#endif

[Andre S. Veteran]

1. If you don't want "silly macro tricks" aka include guards then just never include the header more than once, or use #pragma once

 

Include guards are still the only standard way, and not including the header more than once in any compilation unit is a very difficult problem to solve in general.

 

2. Header files are used to define the interface/contract.

Not true, they also must include private class members, inline and template function definitions, among other implementation details. The way to define interfaces in object-oriented languages is to use actual interfaces.

 

Header files in C++ are just a legacy of the C compilation model; it's not coincidence that no other language makes use of them.

 

3. For his problem there is no way the compiler could help him...

I agree; the reliance of C and C++ on pre-processor tricks are but one of several issues that make the compiler and tooling very difficult to make user-friendly. The compiler can't report anything meaningful about macros because it doesn't know anything of macros. Well-designed languages take the feasability of tooling into consideration, which apparently wasn't on Stroustrup's mind back then.

[fatbeerguy]

Include guards are still the only standard way, and not including the header more than once in any compilation unit is a very difficult problem to solve in general.

 

Not true, they also must include private class members, inline and template function definitions, among other implementation details. The way to define interfaces in object-oriented languages is to use actual interfaces.

 

Header files in C++ are just a legacy of the C compilation model; it's not coincidence that no other language makes use of them.

 

I agree; the reliance of C and C++ on pre-processor tricks are but one of several issues that make the compiler and tooling very difficult to make user-friendly. The compiler can't report anything meaningful about macros because it doesn't know anything of macros. Well-designed languages take the feasability of tooling into consideration, which apparently wasn't on Stroustrup's mind back then.

 

For interfaces yes you could use something like

 

class IMyInterface 

{

public:

 virtual ~IMyInterface() { }

 virtual void the_magic() = 0;

};

But if you required data members you wished to be hidden then you can use the PIMPL idiom, but either way someone seeing some basic types or forward declared internal classes in the private section isn't too bad.

[Andre S. Veteran]

I know, my point is that header files are not interfaces or contracts, because they expose implementation details. Heck the entire STL is implemented in headers. They're a compiler convenience and a programmer inconvenience.