class problems!!

[Smithy006]

Hi There,

I have a class called person...

class person //define person class
{
int currentfloor;
int destfloor;
char name [10];


public:
//Come in creates 20 people instances
void come_in(void);
void exit(int num);

person:erson()
{
static int count = 0;
const int recordlength = 16;

//load a person from person.txt and store them
ifstream infile;
infile.open("person.txt");
if(!infile.fail())
{
cout << "initialising person " << count+1 << "..." << endl;
infile.seekg(recordlength*count++, ios::beg);
infile >> name >> currentfloor >> destfloor;
infile.close();
}
else
{
cout << "File not found..." << endl;
cout << "Fatal error..." << endl;
cout << "Terminating program..." << endl;
//How can I terminate the program from here??
}
}


};

My question is how can I terminate my program when there is an error in person:erson? i have tried to pass a number through person::exit
which changes elevator1.closed (elevator is another class in my program) however, the compiler says that it's an undeclared idetifier.

I've included my source in a zip file to show u what i mean in more detail.

Any help would greatly be appreciated!

Thanks

Regards,

Smithy.

[parksie]

The best idea is to throw an exception, since constructors cannot return values. For example:

class Thing {
public:
    Thing(int x) {
        if(x > 5) throw "Too big";
    }
};

int main() {
    Thing *pThat;

    try {
        pThat = new Thing(6); // Throws exception
    } catch(char *pException) {
        cout << "Error: " << pException << endl;
        return -1;
    }

    cout << "Worked" << endl;

    return 0;
}

[Smithy006]

Thanks.

Just one final question, if I want to make 20 instances of the person class what's the best way to do it?

is there a more effective way then just

person person1;
person person2;
person person3;
person person4;
person person5;
etc..


Regards,

Smithy.

[crptcblade]

yup, make an array

person persons[20];

indexes for this example will start at 0 and go to 19.

[Smithy006]

Thanks.

How do I make a member function call that applies to all of the person arrays?

i.e. how do i call person::something

that will apply to all of the arrarys so i can access the private data from each array in the person::something member function.

Thanks.

Regards,

Smithy.

[Smithy006]

just to explain my problem a little furthur...

void elevator:pen_doors(void)
{
//Check if people need to come aboard, if so aboard them.
cout << "Getting On : ";
for (int i = 0; i ==19; i++)
{
person::get_on(i,level);
}
}

note: level is a priv int in elevator.

I keep getting the compiler error:
error C2352: 'person::get_on' : illegal call of non-static member function

get_on in the person class is public and is defined as:
void get_on(int, int);


Any help would greatly be appreciated!

Thanks!

Rgards,

Smithy.

[parksie]

The class itself doesn't know how many instances there are, so you can't do this. And anyway, a static member function is not allowed access to the internal data because the compiler doesn't know which instance you mean.

How about passing a pointer to the array and seeing how that goes?

[Smithy006]

cool, thanks for that, if it's not too much trouble could u gives us a quick sample on how doing it with a pointer might work?

thanks

[parksie]

Well, I'm not sure about the way you're going about it, design-wise, but here's one way...sorta ;-)

void elevator::open_doors(person *pPeople, int iCount) {
    //Check if people need to come aboard, if so aboard them.
    cout << "Getting On : ";
    for (int i = 0; i < iCount; ++i) {
        get_on(&(pPeople[i]));
    }
}

void elevator::get_on(person *pPerson) {
    cout << pPerson->some_member_data << " has just got on the elevator" << endl;
}

void somecode() {
    elevator e;
    person people[20];

    e.get_on(people, 20);
}

[Smithy006]

Thanks again parksie

However, I'm still a little lost with it. I have included an updated version of my code in this zip. If possible could you sorta have a look at this and tell me how to use the pointers a little better.
Thanks again for all of your help