increasing the size of an array of objects

[fpsasm]

Hello,
I've made a program that uses an array of objects, it's work well so far, upto the point that I try to increase the size of an array.

So, in main the relevant code loops like this:

int main(){
        /* classes used */
        phoneBook *p;
....
        numLines = 0;
....

        /*
                findNumLines, finds the amount of lines present
                in the buffer.
                Then  p=... creates an array of objects
                of size 'numLines'
                                                                */
        findNumLine(buffer,numLines);
        p = new phoneBook[numLines];

        getLine(buffer, p);

        /*
                Everything works upto here!
               
                                                       */
....
                /*IO requests take place and this function is called */

                        addEntry(p, numLines);
....
}

The addEntry is an IO function, it requests for a user input, puts it into a temp-values. addEntry then calls "increaseArraySize" to increase the size of p!

void addEntry(phoneBook *p, int &numLines){
.....
/*numlines is now 3. there is an array of objects that has
**numLines amount of objects*/
     increaseArraySize(p, numLines, 1);
//numlines is now 4
     printAll(p, numLines); //error occurs here!
....

}

So at this point, an error occurs. The increaseArraySize function, creates a temp array of objects (t). all the information in p, is copied into t. p is destroyed, and created to a new size, the new array p is populated with the info in t, and then t is deleted.

void increaseArraySize(phoneBook *p, int &numLines, int a){
        /* temp */
        phoneBook *t;

        numLines += a;
        t = new phoneBook[numLines];

        for(int i = 0; i < (numLines-a); i++){
                t[i] = p[i];
        }

        t[numLines-a].setNull();
        printAll(t, numLines);

        cout << "Numlines is:" << numLines <<endl;

        /* delete p and re-init */
        delete [] p;
        p = new phoneBook[numLines];

        printAll(t, numLines);
        printAll(p, numLines);


        p=(t);
        cout <<"------------------t--------------"<<endl;
        printAll(t, numLines);
        cout <<"------------------p--------------"<<endl;
        printAll(p, numLines);

        /* delete temp array of objects */
        delete [] t;
}

The printAll function prints out all the objects in the array. The print outs are correct, and are the same. This function seems to work...

THE PROBLEM
The problem is, back in the addEntry() function, the values of the objects of p aren't the same as the objects of p in the increaseArraySize() function (after deleting it and recreating it (it, as in p)).

I guess, that I'm doing the resizing incorrectly.. but i'm not sure what else to do?..

It's long winded, but I much appreciate the time you've spent reading so far :)

Thanks,
Matthew

[arkoenig]

Why aren't you using a vector?

[fpsasm]

Why aren't you using a vector?

Well, I'm new to C++, I do recall someone saying not to use realloc, but instead making a temp value to store info into, and then re-creating the initial array, just bigger.

I thought vectors were for ints, floats doubles. I'm using strings

:)

[Moschops]

A vector is marvellous. It is for any object you care to define.

vector<int> someVector; // vector of ints
vector<crazyStructure> someOtherVector; //vector of crazy structures

Anything you like. Go nuts with it. :)

[chrjs]

Although if you don't want to use vectors, the problem probably is that at line 26, you are changing the value of the local variable p in the function increaseArraySize, which doesn't change the value of the p in addEntry. You should pass p as a reference like void increaseArraySize(phoneBook *& p, int &numLines, int a)

[fpsasm]

Although if you don't want to use vectors, the problem probably is that at line 26, you are changing the value of the local variable p in the function increaseArraySize, which doesn't change the value of the p in addEntry. You should pass p as a reference like void increaseArraySize(phoneBook *& p, int &numLines, int a)

I don't see how this would be a problem (passing *p). Prior to the addEntry(), i pass p to a function that accepts a (phoneBook *p), it manipulates it, and the change is seen in main.

[fpsasm]

Hello,
I've made a program that uses an array of objects, it's work well so far, upto the point that I try to increase the size of an array.

So, in main the relevant code loops like this:

int main(){
        /* classes used */
        phoneBook *p;
....
        numLines = 0;
....

        /*
                findNumLines, finds the amount of lines present
                in the buffer.
                Then  p=... creates an array of objects
                of size 'numLines'
                                                                */
        findNumLine(buffer,numLines);
        p = new phoneBook[numLines];

        getLine(buffer, p);

        /*
                Everything works upto here!
               
                                                       */
....
                /*IO requests take place and this function is called */

                        addEntry(p, numLines);
....
}

The addEntry is an IO function, it requests for a user input, puts it into a temp-values. addEntry then calls "increaseArraySize" to increase the size of p!

void addEntry(phoneBook *p, int &numLines){
.....
/*numlines is now 3. there is an array of objects that has
**numLines amount of objects*/
     increaseArraySize(p, numLines, 1);
//numlines is now 4
     printAll(p, numLines); //error occurs here!
....

}

So at this point, an error occurs. The increaseArraySize function, creates a temp array of objects (t). all the information in p, is copied into t. p is destroyed, and created to a new size, the new array p is populated with the info in t, and then t is deleted.

void increaseArraySize(phoneBook *p, int &numLines, int a){
        /* temp */
        phoneBook *t;

        numLines += a;
        t = new phoneBook[numLines];

        for(int i = 0; i < (numLines-a); i++){
                t[i] = p[i];
        }

        t[numLines-a].setNull();
        printAll(t, numLines);

        cout << "Numlines is:" << numLines <<endl;

        /* delete p and re-init */
        delete [] p;
        p = new phoneBook[numLines];

        printAll(t, numLines);
        printAll(p, numLines);


        p=(t);
        cout <<"------------------t--------------"<<endl;
        printAll(t, numLines);
        cout <<"------------------p--------------"<<endl;
        printAll(p, numLines);

        /* delete temp array of objects */
        delete [] t;
}

The printAll function prints out all the objects in the array. The print outs are correct, and are the same. This function seems to work...

THE PROBLEM
The problem is, back in the addEntry() function, the values of the objects of p aren't the same as the objects of p in the increaseArraySize() function (after deleting it and recreating it (it, as in p)).

I guess, that I'm doing the resizing incorrectly.. but i'm not sure what else to do?..

It's long winded, but I much appreciate the time you've spent reading so far :)

Thanks,
Matthew

Yes... well, I haven't figured out the exact cause. But this works:

working code

void increaseArraySize(phoneBook *&p, int &numLines, int a){
        phoneBook *t;
        numLines += a;
        t = new phoneBook[numLines];
        int kl;
        for(kl = 0; kl < (numLines-1); kl++){
                        t[kl].copyObj( p[kl]);
                }

        delete [] p;

        p =(t);
}

analysis
I've put *&p, rather then *p into the function parameter list. That stops the seg-fault, but it doesn't fix the whole problem.

.copyObj() is a function that copies the private members, internally, the result is the same. But it works, now.

I didn't do a delete [] t either, if I do it clonks out an error. So that's left out.

Thanks for all the help.. Cheers