Thread: Double Pointer, dynamic allocation help

If you are permitted to do so, use a std::vector<std::shared_ptr<Room>> instead of a Room**. It is possible that shared_ptr is not yet available in the standard library that you can use, in which case use a std::vector<Room*>, then get your Hotel class to manage the memory for the Room pointers.

Whether you use a std::vector<Room*> or have to stick with Room**, note that once you do manual memory management, you need to care about the copy constructor, copy assignment operator and destructor. It seems that you did declare (and presumably defined) the destructor, but you should also define the copy constructor and copy assignment operator or declare them private to disable them.

Now, concerning the code that you showed. This is wrong:

Code:

Room[c] = new *Penthouse;

It should be:

Code:

Room[c] = new Penthouse;

Furthermore, look carefully at the placement of the return statement in the setHotelRooms member function. Since the return statement is unnecessary here, I suggest that you remove it. Incidentally, if you want to specify that a function takes no arguments, just leave its parameter list empty as it is not common C++ style to use the void keyword for that purpose.

By the way, getHotelID sounds like it should be a const member function.

It should be

Code:

rPoint[c] = new Penthouse;
//etc.

(But why are your rooms called points?)

And (if you have your heart set on not using a vector, etc) why not just declare rPoint as an array of MAX_SIZE pointers in the first place?

Originally Posted by Trey Brumley

by removing one of the asterisks for Room **room because it was unnecessary

A Room** may be necessary since a hotel will presumably have rooms of different subtypes. With just a Room*, you would be allocating a dynamic array of objects of a single subtype (unless you're going with say, a linked list approach, which does not seem to be the case here).

To fix the error you get, look carefully at your declaration of setHotelRooms in the header and its definition in the source file. The function signature should match.

Now in the main program, I'm getting a bunch of error C2228s (function must have a class/struct/union) for class Room, and all the Room identifiers are listed as undeclared.

For example,

Code:

charge = hotel.*room[rn].calculateBill(hotel.*room[rn].getNights(), hotel.*room[rn].getOccNum(), hotel.*room[rn].getBaseRate(), hotel.*room[rn].getAddRate());

In the above case, "left of '.calculateBill' must have class/struct/union." and "'room' : undeclared identifier"

Room.h

Code:

class Room    {
    private:
        int occNum;
        int nights;
        int MaxOccNum;
        double baseRate;
        double addRate;
        bool smoking;


    public:
        Room(void);
        ~Room(void);
        Customer customer;
        void setSmoking(int i, int s);
        bool isOccupied();
        bool isSmoking();
        int getNights();
        void setNights(int days);
        int getOccNum();
        void setOccNum(int ppl);
        int getMaxOccNum();
        void setMaxOccNum(int max);
        double getBaseRate();
        void setBaseRate(double rate);
        double getAddRate();
        void setAddRate(double add);
        double calculateBill(int night, int occNum, double rate, double add);
        void assignCustomer(string nm, string cc, bool emp);
        void modify();
        void clearRoom();
    };

Room.cpp

Code:

Room::Room(void){
};


Room::~Room(void)
{
};


void Room::setSmoking(int i, int s)
{
    if (i <= s)
        smoking = true;
    else
        smoking = false;


    return;
}


bool Room::isSmoking()
{
    return smoking;
}


int Room::getNights() {return nights;};


void Room::setNights(int days)
{
    nights = days;
    return;
};


int Room::getOccNum() { return occNum; };


void Room::setOccNum(int ppl)
{
    occNum = ppl;
    return;
};


bool Room::isOccupied()
{
    return (getOccNum() > 0);
}


double calculateBill(int night, int occNum, double base, double add)
{
    double charge;
    double addRate = add*(occNum-1);
    charge = addRate+base; 
    charge = charge*night;


    return charge;
}


//In case a room needs to be modified (e.g. add nights or occupants), this function enables that.


void Room::assignCustomer(string nm, string cc, bool emp)
{
    customer.setName(nm);
    customer.setCCNum(cc);
    customer.setEmployee(emp);
    return;
}


void Room::clearRoom()
{
    customer.setName("");
    customer.setCCNum("");
    customer.setEmployee('N');
    setOccNum(0);
    setNights(0);


    return;
}


int Room::getMaxOccNum()
{
    return MaxOccNum;
}


void Room::setMaxOccNum(int max)
{
    MaxOccNum = max;
    return;
}


double Room::getBaseRate()
{
    return baseRate;
}


void Room::setBaseRate(double rate)
{
    baseRate = rate;
    return;
}


double Room::getAddRate()
{
    return addRate;
}


void Room::setAddRate(double add)
{
    addRate = add;
    return;
}

I do not see include for your header file in the cpp file

Originally Posted by Trey Brumley

In the above case, "left of '.calculateBill' must have class/struct/union." and "'room' : undeclared identifier"

That is because you are using the wrong syntax for what you want to do. You probably want to dereference the member pointer, but you are using syntax that looks like you are dereferencing a pointer to the member instead.

With a Room**, I would expect:

Code:

charge = hotel.room[rn]->calculateBill(hotel.room[rn]->getNights(),
                                       hotel.room[rn]->getOccNum(),
                                       hotel.room[rn]->getBaseRate(),
                                       hotel.room[rn]->getAddRate());

With a Room*, this will do:

Code:

charge = hotel.room[rn].calculateBill(hotel.room[rn].getNights(),
                                      hotel.room[rn].getOccNum(),
                                      hotel.room[rn].getBaseRate(),
                                      hotel.room[rn].getAddRate());

Originally Posted by tabstop

If you just have a single star now (ie Room * room), then hotel.*room[rn] does not exist, because hotel.room[rn] is no longer a pointer, but a simple Room.

Not really: the syntax is not appropriate to begin with so it would not have worked either if the member was a Room**.

Should the calculateBill member function really need to have those values passed into it? Seems to me that the function doesn't/shouldn't need anything to be passed in, it can just internally call the member functions (getNights, getOccNum, getBaseRate, getAddRate) to get those values it needs for its calculations.