Initialize an Array of Pointers to Objects

Posted on 2005-02-26
Medium Priority
Last Modified: 2010-08-05

Working on a project that requires the initialization of an array of pointers to objects.

The calling function

      className *arrayPtr = new array [ arraylength];
      for (int j = 0; j < arraylength - 1; j++)
            array[j] = NULL;

However, it doesn't want to compile.  

What would be the best way to make this work?


Question by:theakst
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LVL 37

Expert Comment

by:Harisha M G
ID: 13411684
Hi theakst,
    What's the error message?
    Please give exact code (instead of className, array etc.)


Expert Comment

ID: 13411685
i think what you want is:

   className *arrayPtr = new array [ arraylength];
     for (int j = 0; j < arraylength - 1; j++)
          *array[j] = NULL;

that is assuming that you want what the array points at to be null
the * dereferences the array's address. with out it you are essentially saying the address of array[j]=0 which is not what you want (i think)
LVL 55

Expert Comment

by:Jaime Olivares
ID: 13411687
I think it must be:

     className *arrayPtr = new className[ arraylength];  
If not, please send error message...
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LVL 37

Expert Comment

by:Harisha M G
ID: 13411700
Yes, it should be...
className *arrayPtr = new className[ arraylength];
void *arrayPtr = new className[ arraylength];

Author Comment

ID: 13411755

If I use the *array[j], error msg is as follows:

file.cc: In constructor `className::className()':
file.cc:17: no match for `* obj&' operator

Maybe the error lies in the obj const downstream?

LVL 55

Accepted Solution

Jaime Olivares earned 1000 total points
ID: 13411770
Ok, since you want an ARRAY OF POINTERS TO AN OBJECT, it must be:

className **arrayPtr = new className *[ arraylength];  

Author Comment

ID: 13411803
Thanks Jaime!!
LVL 30

Expert Comment

ID: 13411971
With the above method, you still need to initialize each iteration.

Check out the following link for some good safe and efficient methods for creating a two dimensional array:

The above link also list a wrapper function that can be use as follow:
className **arrayPtr = Allocate2DArray<className >(X_size, Y_size);

It also has an associated function to clear the memory.


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