a class in a struct?

okay, I'm not sure this is legal, but here it goes...

I'm trying to have a struct with a class in it...

main.cpp

Code:

---

...
#include "foo.h"
...
fooStruct foo1;
foo1.bar1.hello();
...

---

foo.h

Code:

---

...
#include "bar.h"
...
struct fooStruct
{
  barClass bar1;
}
...

---

bar.h

Code:

---

class barClass
{
  public:
      void hello();
...

---

it gives me errors in main... I mainly want to know
1) is this legal
2) if so, what am i doing wrong?
thanks in advance...

It is legal. I can't tell what the problem is from the code you posted though. Can you post a bit more, along with the errors?

here's some literal code:

ERRORS: (they get cut off where they are by the compiler :( )
271 C:\TCWIN45\BIN\dev c++\battle system\version 3\main.cpp
request for member `rules' in `game.gamesStruct::dice()', which
272 C:\TCWIN45\BIN\dev c++\battle system\version 3\main.cpp
request for member `run' in `game.gamesStruct::dice()', which is

Main.cpp

Code:

---

...
#ifndef _GAMES_H
#define _GAMES_H
#include "games.h"        //gamesStruct for Merchant Alley
#endif
...
int main(){
...
gamesStruct game;
...                       
if(ans==1)
{
        game.dice.rules();
        game.dice.run();
}
...

---

ALL of games.h

Code:

---

#ifndef _DICE_H
#define _DICE_H
#include "dice.h"
#endif

struct gamesStruct
{
        diceClass dice();        //create instance of dice class
};

---

ALL of dice.h

Code:

---

class diceClass
{
        public:
                diceClass();        //initializer
                void run(char*);        //starts with username
                void rules();        //prints rules
        private:
                void setstats(char*);        //sets stats
                void savestats();        //saves changed stats

                int rolldice();        //returns random number between 1..6
            char username[20];        //holds username
            char password[20];        //holds password
            int hp,atk,def,lvl,exp,mon,pts;        //stats
};

---

and below can be found dice.cpp... it's too big to post...

Ok I downloaded your file and opened it up and this was all that was in it

Code:

---

/*
        games.cpp

        gamesStruct definition/prototype
       
        John Shao
*/

struct gamesStruct
{
        diceClass dice();        //create instance of dice class
};

---

Can you post all your code? From what I can see, the first thing that is wrong is this you are forgetting to include "games.h" in your .cpp file.

next thing is this statment:
diceClass dice(); //create instance of dice class

it should be just this:
diceClass dice

when you declare a stuct or class within anouther class, you don't need the (). Basically what you are doing is calling the constructor for dice and you don't need to.

Code:

---

int main()
{
    gamesStruct game()

    return(0);
}

---

diceClass will call its constructor on its own when game is created

also, in the code that you posted here, it looks like you declared gamesStruct in the games.h file but it is also declared in the games .cpp file I downloaded. if you declared it twice then you will get a lot of errors. The complete code you have so far will show us what you actually have going on so if you can post it I will try to help you.

okay, it's quite a bit of code that doesn't have anythign to do with this, but here it is:

main.cpp

games.h

dice.h

dice.cpp

hmm ... where should I start. Like I said in my previous post, You have this

Code:

---

struct gamesStruct
{
        diceClass dice();        //create instance of dice class
};

---

declared twice. Once in the games.h file and once in the game.cpp file. And you don't need ( ) after you declare a diceClass variable inside a stuct or a class.

I cant compile the code because of missing header files but I do know you don't need all those #ifndef #define statements in your .cpp file. It only has to be done in the header files like so:

Code:

---


/******** dice.h header file **********/
#ifndef _DICE_H
#define _DICE_H

// header file stuff here

#endif

---

then just #include header normally in your dice.cpp file. or whereever you need to include that header file. You also don't have to check the standard heads the way you are either. They are already defined the first time your program hits the first #include <iostream> it finds. I know you know this from your comments in your code but I am just letting you that you don't have to do this:

Code:

---

#ifndef _iostream_h
#define _iostream_h
#include <iostream>       
#endif

---

that is all I found just having a quick look. Like I said, I couldn't get it to compile because of the missing header file so I can't really help you any more than what I have.

>> I do know you don't need all those #ifndef #define statements in your .cpp file. It only has to be done in the header files like so... then just #include header normally in your dice.cpp file.

I know, but I just kinda like this way better... I don't remember why I started putting all those unnecessary checks in, but it just kinda became habit for me... idk...

also, there is no longer any games.cpp file.. it's only games.h, which is #included in main.cpp... and only contains this:

Code:

---

#include "dice.h"
struct gamesStruct
{
        diceClass dice();        //create instance of dice class
};

---

Code:

---

#include "dice.h"
struct gamesStruct
{
        diceClass dice;        //declare instance of dice class
};

---

The gameStruct constructor will create the instance of diceClass, you just need to declare it.

I did, in main.cpp...

yea you did declare it in main.cpp but this is what your games.h file contains(well the one I downloaded anyways):

Code:

---

struct gamesStruct
{
        diceClass dice() ;        //create instance of dice class
};

---

notice the red part.

I am not sure if you are seeing what is wrong with this stuct. It should look like this:

Code:

---

struct gamesStruct
{
        diceClass dice;        //create instance of dice class
};

---

Notice the lack of red.
maybe you just missed it and didnt notice that you have added parentheses after you delcare dice in your gamesStruct

oic... thanks alot... I completely missed that in an earlier post... it was just the way that Zach L. worded it that threw me off...

Sorry 'bout that.

Quote:

---

Basically what you are doing is calling the constructor for dice and you don't need to.

---

Are you sure about that? As I recall from some book somewhere (I'm sure everyone knows what book I'm talking about :D:p), struct is 99% the same as class except that things are public by default, so it actually looks to me like your declaring a function called dice() that returns a diceClass.

Quote:

---

Are you sure about that?

---

Damn your right. Its not a constructor call.I'm not sure what my compiler is seeing it as but it sure isn't a class. Will the compiler see it as a function that takes an unknown number of arguments? The only good thing is that when you try to use it, it will fail. I tried this code:

Code:

---

#include <iostream>

using namespace std;

class barClass
{
  public:
      void hello()
      {  cout<<"Hello. This is a test.\n";  }
};

struct Foo
{
  public:
      barClass bClass();
};

int main(int argc, char *argv[])
{
  Foo fooFoo;

  fooFoo.bClass.hello();

  return(0);
}

---

and got the compiler error telling me:

Quote:

---

error C2228: left of '.hello' must have class/struct/union type

---

So it looks like you are right Hunter2. I though that declaring a function without any arguments is only allowed in C.

Quote:

---

I though that declaring a function without any arguments is only allowed in C.

---

Now how this might happen, I'm not sure :D Unless you mean "int function(void);". If you want to declare an object of barClass, you simply go "barClass bClass;" and it will automatically use the default constructor (i.e. the one that has no arguments), unless the Foo constructor explicitly initializes it using one of the constructors that takes arguments. Example:

Code:

---

Foo::Foo()
:bClass(theArgumentYouWantToUse)
{
    //do something
}

---

Quote:

---

Now how this might happen, I'm not sure Unless you mean "int function(void);

---

No I mean int function() or are you telling me that a function with no arguments specified defaults to void in c++?(Just as an added note, VC++ sees it as void).I just want this cleared up so I know what the standard is for function prototypes in c++ because right now I am under the impression that all functions have to specify an argument even if it is void.


I did some searching and found out that in C
int function( );
is deemed to take an unknown number of arguments.(from the FAQ on this site) But this same statement is interpreted in C++ as a prototype equivalent to the following:
int function(void );
Guess thats what happens when you always prototype functions. I had forgotten all about that but there it was in black and white in one of my c++ programming books.

C does (or at least did) have that convention, where
int f( ) is unknown number of args
int f(...) is the C++ equivalent

In C++,
int f( ) and
int f(void)
are the same.

Really? I didn't know that. I always thought that not specifying any arguments meant just zero arguments for both languages... I learn something new every day :)

Looks like we both did. I always thought that in c++ all function arguments had to be specified, even if the dont' take any.