Array of class and a pointer to it

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Eitan - 04 May 2005 01:13 GMT

Hello,

I defined a class name MyClass.

I would like to define an array of 4 by 8 of that class.
I would like to define a pointer to the array of MyClass.

I tried it with static definition:
MyClass m_MyClass[4][8] ;
I can not seem to find the way to define a pointer to this array?!?!?

I tried also to define it with the new operator but had similar results.

Any ideas how to do it?

Eitan

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Boni - 04 May 2005 13:43 GMT

How about
MyClass ** ppMyClass;
ppMyClass=m_MyClass; or the same
ppMyClass=&m_MyClass[0][0];
or dynamically
MyClass ** ppMyClass=new MyClass *[4]
for (int i=0;i<8;++i){
ppMyClass[i]=new MyClass [8]
}

Don't forget to do the same when you delete (not just delete[]ppMyClass)
Hope it helps,
Boni

> Hello,
>
[quoted text clipped - 12 lines]
>
> Eitan

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Brian Muth - 04 May 2005 22:25 GMT

> How about
> MyClass ** ppMyClass;
> ppMyClass=m_MyClass; or the same

No, the above line is invalid.

> ppMyClass=&m_MyClass[0][0];

and this line is also invalid.

> or dynamically
> MyClass ** ppMyClass=new MyClass *[4]
> for (int i=0;i<8;++i){
> ppMyClass[i]=new MyClass [8]
> }

Ah, but that's not the same, is it? You have created an array of pointers,
not a two-dimensional array, which is what the OP wants.

Brian

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Boni - 05 May 2005 17:55 GMT

> No, the above line is invalid.
> and this line is also invalid.

Hi Brian,
thanks to pointing that out. I am sorry for that advice.

> Ah, but that's not the same, is it? You have created an array of pointers,
> not a two-dimensional array, which is what the OP wants.

I think you are wrong on that. There is physically no such thing as a 2
dimentional array in the memory. It is array of pointers to pointers. The
first operator[] take the pointer to the array of values the second
operator[] takes the value.
With best regards,
Boni

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Brian Muth - 05 May 2005 22:27 GMT

And thank YOU for refreshing by C skills!

Brian

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Brian Muth - 04 May 2005 19:53 GMT

MyClass (*m_MyClass)[4][8];

Brian

> Hello,
>
[quoted text clipped - 12 lines]
>
> Eitan

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Eitan - 04 May 2005 21:10 GMT

Thanks, Eitan

> Hello,
>
[quoted text clipped - 12 lines]
>
> Eitan

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