basic classes question

[pauldepstein@att.net]

Suppose I have a class of objects which take an integer parameter.

I can easily create an object with the required parameter as follows:

name_of_class variable_name(i nteger_value);

For clarity, suppose I have a bank-account class and each object falls
into one of 5 distinct categories.

Then I might have code like:

bank_account object_1(5);

bank account object_2(3);


But if I have lots of objects of the class, I don't know what the
correct syntax is for doing such assignments (creating the objects) in
a loop.

Would the following work? (By using a giant leap of imagination, let
my_integer_valu ed_function denote an integer_valued function.)

object_array = new bank_account[n];

for (i=0; i<n; i++)

bank_account object_array[i] (my_integer_val ued function of i);


Or perhaps it should be

object_array = new bank_account[n];

for (i=0; i<n; i++)

object_array[i] (my_integer_val ued function of i);

Thanks for all your help and advice. I have received a lot of help
from this group.

Paul Epstein

[Neelesh Bodas]

Re: basic classes question


pauldepstein@at t.net wrote:[color=blue]
> Suppose I have a class of objects which take an integer parameter.
>
> I can easily create an object with the required parameter as follows:
>
> name_of_class variable_name(i nteger_value);
>
> For clarity, suppose I have a bank-account class and each object falls
> into one of 5 distinct categories.
>
> Then I might have code like:
>
> bank_account object_1(5);
>
> bank account object_2(3);
>
>
> But if I have lots of objects of the class, I don't know what the
> correct syntax is for doing such assignments (creating the objects) in
> a loop.
>
> Would the following work? (By using a giant leap of imagination, let
> my_integer_valu ed_function denote an integer_valued function.)
>
> object_array = new bank_account[n];
>
> for (i=0; i<n; i++)
>
> bank_account object_array[i] (my_integer_val ued function of i);
>[/color]

No
[color=blue]
>
> Or perhaps it should be
>
> object_array = new bank_account[n];
>
> for (i=0; i<n; i++)
>
> object_array[i] (my_integer_val ued function of i);[/color]

No.
When you use operator new[], all objects get constructed using the
no-arg constructor.
If you want to construct all objects with a different initial value,
use array of pointers, and allocate in a loop.

const int n = 100;
bank_account* object_array[n];

for(int i=0; i < n; i++)
{
object_array[i] = new bank_account(i) ; // initailze with i.
}

Also, prefer std::vector over arrays.

Hope this helps.

[pauldepstein@att.net]

Re: basic classes question


Neelesh Bodas wrote:[color=blue]
> pauldepstein@at t.net wrote:[color=green]
> > Suppose I have a class of objects which take an integer parameter.
> >
> > I can easily create an object with the required parameter as follows:
> >
> > name_of_class variable_name(i nteger_value);
> >
> > For clarity, suppose I have a bank-account class and each object falls
> > into one of 5 distinct categories.
> >
> > Then I might have code like:
> >
> > bank_account object_1(5);
> >
> > bank account object_2(3);
> >
> >
> > But if I have lots of objects of the class, I don't know what the
> > correct syntax is for doing such assignments (creating the objects) in
> > a loop.
> >
> > Would the following work? (By using a giant leap of imagination, let
> > my_integer_valu ed_function denote an integer_valued function.)
> >
> > object_array = new bank_account[n];
> >
> > for (i=0; i<n; i++)
> >
> > bank_account object_array[i] (my_integer_val ued function of i);
> >[/color]
>
> No
>[color=green]
> >
> > Or perhaps it should be
> >
> > object_array = new bank_account[n];
> >
> > for (i=0; i<n; i++)
> >
> > object_array[i] (my_integer_val ued function of i);[/color]
>
> No.
> When you use operator new[], all objects get constructed using the
> no-arg constructor.
> If you want to construct all objects with a different initial value,
> use array of pointers, and allocate in a loop.
>
> const int n = 100;
> bank_account* object_array[n];
>
> for(int i=0; i < n; i++)
> {
> object_array[i] = new bank_account(i) ; // initailze with i.
> }
>
> Also, prefer std::vector over arrays.
>[/color]
Thanks.

I find const int n = 100 to be a bit inflexible.

I can't get this to work in the case of variable n. Since arrays need
to have constant integer bounds, it seems I need a pointer to a
pointer.

I somehow can't get this to work.

Thanks for your continued help.

Paul Epstein