Dynamic Array sizing

[mattKnight]

There must be a "standard" way of doing this...

Suppose I have a class, which I allocate on the heap

MyClass * pMyClassInst[5];

pMyClassInst[0] = new MyClass

The above limits me to having 5 instances on MyClass.

How can I size or resize that array pMyClassInst as runtime?

What do I need to read up? As you can tell I a little new to C++!!



Take Care

Matt
If at first you don't succeed, skydiving is not for you.

 

[LazyMe]

Sizing is easy:
Don't say it's 5, just say it's X. And set X to whatever suits your needs at runtime.

Resizing involves just a bit more work:
For example; you could use malloc and realloc to store pointers to the classes in a block of memory that's resizable.


Greetings,
Rick

 

[xwb]

Try using vectors or lists

#include <vector>
typedef std::vector<MyClass*> MyClassVec;

MyClassVec pClassInst;

// To add a new one
pClassInst.push_back(new MyClass);

It is the same for lists except you cannot address them as pClassInst[x].

 

[BoulderBum]

Just to add to the confusion, I'll contribute the modern standard dynamic memory allocation method (using operators 'new' and 'delete').

//declare variables
int n = 5;
MyClass *pMyClassInst;

//size it at run-time... creates an array of 'n' size
pMyClassInst = new MyClass[n];


As you may know, when you use dynamic memory allocation in your program, you need to manually reclaim the memory using operator delete when you are through with the object(s). To delete an array, use delete with '[]'.

//delete the array you created
delete[] pMyClassInst;

Resizing can be acheived by creating a new array dynamically, then copying the old information before deleting the original array, but as XWB suggests, you may also use STL templates which will do all of this for you behind the scenes.

Hope that helps!

 

[xwb]

Note Bolderbum's suggestion will only work on C99 compilers.