pointer to class object

[ceodav]

Hi,
i use an array af class object like the follow but i'm misunderstanding something...


if i write

Cnet *R[100];

for(int i=0; i<100; i++)
{
R = new CNeuralNet;

}

and then inside the destructor

for(int i=0; i<100; i++)
{
delete R;
}

it works fine and when i call the object

r->....

infact i don't get any error...

but if i write

Cnet *R;
R = new CNeuralNet [100];

and then inside the destructor

delete[] R;

i get errors when i call the functions inside the class i created

r->....


the error is :

error C2819: type 'Cnet' does not have an overloaded member 'operator ->'
: see declaration of 'Cnet'


Where is the problem?


thanks
D.

 

[globos]

In the first version of your code, R is an array of pointers on Cnet instances.
So

R[i]

is of type Cnet* , and you have to write

R[i]->do_somthing ();

to call routines on that item.

In the second version, R is just a pointer on a Cnet instance, and you want to use that pointer as an array like the previous one. You could also write :

 Cnet R[100];//don't have to delete anything

So

R[i]

is of type Cnet , and you have to write

R[i].do_something ();

to call routines on that item.
That's why you get an error when writing

R[i]->...

.
Notice that you don't have to delete instances in the second version, but just the array.

If you want to use array of instances, I advise you to use class vector from STL.

--
Globos

 

[Cagliostro]

1. to free correctly an array of objects you should do like this:
for(int i = 0; i < 100; i++)
{
delete R;
}
delete[] R;

2. if is declared R as XXX R[yy] you can not
delete[] R; and you can not initialize R to another array like
R = anotherarray; because it is a constant array.
so you can do
XXX* R;
R = new XXX[100];
for(i = 0 ; i < 100.... initialize R

and in destructor delete like is writen above in 1.
[/code]


Ion Filipski

 

[Cagliostro]

1. to free correctly an array of objects you should do like this:    
    for(int i = 0; i < 100; i++)
    {
        delete R[i];
    } 
    delete[] R;

2. if is declared R as XXX R[yy] you can not 
delete[] R; and you can not initialize R to another array like 
R = anotherarray; because it is a constant array.
so you can do 
XXX* R;
R = new XXX[100];
for(i = 0 ; i < 100.... initialize R[i]

and in destructor delete like is writen above in 1.

Ion Filipski