Class inside a struct

Question

I am getting flustrated with two errors and I have absolutely no idea what is wrong.

#ifndef ListElements
#define ListElements

#include "RentalObjects.h"

struct RentalList{
ObjectBase* content;
RentalList* Next;
};
#endif

All the time I get this error:

Error 1 error C2143: syntax error : missing ';' before '*'

Error 2 error C4430: missing type specifier - int assumed.

The RentalObjects.h file features a declaration of the ObjectBase class, which looks as follows:

class ObjectBase{
protected:
    char Make[16];
    char Model[16];
    int Year;
    float PricePerDay;
    Booking* Availability;
public:
    void SetMake(char* value);
    void SetModel(char* value);
    void SetYear(int value);
    void SetPrice(float value);
    bool DisposeBookings();
    bool Book(int Start,int End);
    char* GetMake();
    char* GetModel();
    int GetYear();
    float GetPrice();
    ~ObjectBase();
};

I'd be grateful for a tip.

Most likely you missed a ; at the end of one of a class definition (or somewhere else) inside RentalObjects.h, or otherwise caused ObjectBase to be undeclared due to a syntax error — wakjah
– wakjah, Commented Dec 9, 2014 at 0:19
can we see the whole RentalObjects.h ? does it have include guards? does it include something else? maby recursive includes? — sp2danny
– sp2danny, Commented Dec 9, 2014 at 0:22
Sure, I had multiple classes in it but now I removed them, so take a look: pastebin.com/WQfJuCah — Holger
– Holger, Commented Dec 9, 2014 at 0:26
What is this "Booking" thing? Learn to forward-declare but not define pointed-to classes. You don't need to know what a "Booking" to define your class ObjectBase. Similarly, you don't need to know what an "ObjectBase" is to define your class RentalList. Just forward declare. #including the files that define those classes will inevitably get you into a circular mess. — David Hammen
– David Hammen, Commented Dec 9, 2014 at 0:32

sp2danny · Accepted Answer · 2014-12-09 00:37:32Z

1

When declaring pointers or references, you don't need the whole class/struct definition.

Instead of:

#include "RentalObjects.h"

struct RentalList {
    ObjectBase* content;
    RentalList* Next;
};

you could do:

class ObjectBase;
struct RentalList {
    ObjectBase* content;
    RentalList* Next;
};

this could get you out of a circular include, which might be what's causing your broblem

answered Dec 9, 2014 at 0:37

sp2danny

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3 Comments

Holger Over a year ago

I did as you suggested and it sadly didn't help. Moreover all headers are #ifndef secured so I suppose it should get circularly included (I'm guessing).

sp2danny Over a year ago

make sure you are breaking all circular references. the include guard protects you from infinite loop in the compiler, but it still wont work, the second time a header tries to be included, it wont be, and the symbols wont be defined

Holger Over a year ago

Ok, you were right, it worked finally. Thanks a lot!

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