I''ve started working on an rpg and I have come to a huge problem. It needs to handle all kinds of items and world entities, and I want to have them in llists. The problem is that I have a class torch(just an example) that looks like this: class torch { public: void update(); private: bool lit; int fuel; } void torch::update() { if(lit == true) { fuel--; } if(fuel == 0) { lit == false; } } and I have a llist like this: typedef struct { void *data; void *prev; void *next; } LList; and I do this: LList *entitylist; entitylist->prev = NULL; entitylist->next = NULL; entitylist->data = (torch *)malloc(sizeof(torch)); entitylist->data->update(); vc++ says "left of ->update must point to class/struct/union", can someone PLEASE help me. This is VERY important.

That''s because LList::data is of type void*. Void* does not know what it points to, it does not know that it actually points to a class with update() method.
Simpliest way to solve this is to typecast LList::data to correct type:

  ((torch*)(entitylist->data))->update();  

It is also the wrong way to do it. It won''t solve the problem in the long run. Imagine you add a second object type... umm, beer mug. So, when you traverse your list you won''t know which node points to which object. To solve this you declare a base class with a virtual update() method and inherit all your entities from it:

  class CEntity{public:    virtual void update() = 0;    // = 0 means it''s a pure virtual,    // cannot be instantiated    // can only be used as a base for some other class};// torch is an entityclass torch : public CEntity{public:    virtual void update();private:    bool lit;    int fuel;};void torch::update(){    if(lit == true) {        fuel--;    }    if(fuel == 0) {        lit == false;    }};// CBeerMug is an entity tooclass CBeerMug : public CEntity{public:    virtual void update();private:    void Refill() { // code here }    void Sip() { // code here }private:    long    m_lBeerLeft;};void CBeerMug::update(){    if(m_lBeerLeft <= 0)        Refill();    Sip();}// both torch and CBeerMug are of type CEntity// so, if you have a pointer to CEntity// it can point to any class inherited from// CEntity, either torch or CBeerMugCEntity* pEntity = new torch;pEntity->update();delete pEntity;pEntity = NULL;pEntity = new CBeerMug;pEntity->update();delete pEntity;pEntity = NULL;  

This might not compile as is, but it should give you an idea.

You also might want to consider changing next and prev pointers to LList*. Using void* pointer is not type safe, avoid it if you can.

A couple more things:
- make sure you allocate list node before you use it
- you should use new new/delete to allocate/deallocate classes, not malloc/free.

Happy coding!

first of all, thank you very much for the code. I''m a little new to c++(not C, just c++) and it may take a while before I fully understand what you have told me.

Second, *before* I posted this, I fixed LList to be:

typedef struct {
void *data;
LList *prev;
LList *next;
} LList;

Third, what did you mean by "you should use new new/delete to allocate/deallocate not malloc/free", I don''t know what you are talking about. How do I use new/delete?

new and delete are two operators in C++ that replace C''s malloc() and free(). I find they (new and delete) are much better/more reliable/don''t cause as many problems/cause as many access violations as malloc and free.

  int *foo = new int; // Allocate mem//use foo heredelete foo; // clear memory  

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-cow_in_the_well

''When in doubt, empty your magazine.'' - Murphy''s Combat Law