deconstructing with a vector

[bob323]

I have created a vector of objects that I am constantly changing, but I want to have a deconstructor to deallocate a string in each of the objects when I am done using the vector. I wrote a deconstructor but I noticed that it is getting called all over the place- even when I am not done using the memory. Is there something special about vectors that can account for this, and if so how do I deallocate the memory used in the string for each object in a vector?
Any suggestions would be great!

[parksie]

The destructor will be called every time the object is destroyed, but the vector will be doing its own internal memory management, causing your objects to be constructed/destructed more than you expect.

If you have a copy-constructor (operator=) then you can make sure that it's all kept safe

[filburt1]

BTW, destructors never take arguments and follow the format void ~classname().

[parksie]

They can't return values either.

[bob323]

some of that makes sense to me, I can understand how the vector controls its own state as it needs to recopy itself each time its size changes, but are you saying then that I shouldn't worry about deallocating at all? What about when I am finished with the vector, how will I deallocate- or do I need to?

[filburt1]

Theoretically, in most cases, unless you are using pointers, you should never have to make a destructor.

[filburt1]

Originally posted by parksie
They can't return values either.

That's why I said "void".

[parksie]

No, it doesn't even have a return type

[abdul]

Deconstructors have ~ to show that that they dont have any return type (yes Parskie, Not even void)

[parksie]

Quibbling again

Destructors have ~ because that's how you tell it's a destructor and not a constructor. Destructors take no arguments whatsoever (other than the implicit this), and return no values.

[filburt1]

Originally posted by abdul
Deconstructors have ~ to show that that they dont have any return type (yes Parskie, Not even void)

Oh, you're right. I was saying void meaning it didn't return anything, but then void is kinda different.

[abdul]

Is there anything else than Deconstructor that does not return anything - not even void ?

[parksie]

Other than the destructor, only constructors cannot return values.

Well, actually some functions cannot return values because they get interrupted before they reach their exit code (or none in the case of naked functions, which I haven't found much of a use for yet).

[bob323]

the objects in my vector do pointer elements in them, so it seems to me that they would need to be deallocated when they are finished being used... correct?

[kedaman]

Yes, in the destructor you deallocate all memory allocated in the class. Note you don't deallocate objects that was passed to it (that's undermining object orientation) On the pointers holding them you do
delete varname

or

delete[] varname

if varname is a pointer to an array.

[filburt1]

You might want to use the apvector class. It is templated and works fine for me. (I can't believe I'm actually recommending that AP crap )

http://www.collegeboard.org/ap/compu...l/classes.html

[bob323]

THis all being said I am brought back to my original question then... If I have a vector of objects that have as a component say a *char I need to deallocate the memory used by this *char if I use the new operation to allocate memory. But, as the vector is constantly allocating and deallocating to increase its size, how do I perform a final deallocation once I am finished using the vector?

[kedaman]

if your vector was newed from the beginning you can deallocate it with delete. If not it will be deallocated when it runs out of scope. The vector will of course delete it's objects before it deletes itself, that is handled in the vectors destructor.

[Dillinger4]

Now i know why i program in Java.

[kedaman]

Hey! It's not as bad as it looks Once you get how it is and the benefits of them you can screw Java and be happy

[parksie]

Originally posted by bob323
THis all being said I am brought back to my original question then... If I have a vector of objects that have as a component say a *char I need to deallocate the memory used by this *char if I use the new operation to allocate memory. But, as the vector is constantly allocating and deallocating to increase its size, how do I perform a final deallocation once I am finished using the vector?

for(i = 0; i < 5; i++) {
    char *ptr = new char[10 * i];

    myvector.push_back(ptr);
}

// Use the vector, which will handle allocating the variables
// holding the pointers, not your data itself

for(i = 0; i < 5; i++) {
    delete[] myvector[i];
}
myvector.clear(); // Remove invalid pointers

[kedaman]

Hmm, if that's how it is, you should use a string class that knows how to deallocate itself. If you like lowlevel stuff it's of course ok but otherways it's against object orientation in terms of encapsulation.