ifstream issue

[Sefi P]

Hello,

I am using a user-defined struct (not class).
with ifstream::operator>> i am inserting data from a file into a pointer
to this struct, (being the second argument to the >> operator) because the
file states how many structs there are, and their full details. it is an
array whose size depends on the file input.

anyway, it does read and store everything into the array of structs. (the
array is allocated with new, it is not an automatic object), but after returning
the ifstream from the operator>>, the pointer obviously holds nothing.

why?
must i pass a "real" object to such operators?
in past times, i used "real" objects as the second argument which wrote to
their data memebers. however, this is not the case now.

thank you,
Sefi P.

[Sefi P]

Ok,

something has gone terribly wrong.
a very very simple passing pointer to a function, allocating new there, and
returning - does not work!

i don't know what is wrong, it is not connected to the ifstream, anyway.
it is seemingly just fine.

maybe the frigging MFC has to do with this conspiracy..

sefip

[Sefi P]

Riddle solved - sorry, don't bother answering.

it was simply a ** that was required, you can't pass * and "new" on it, you
must pass pointer to this, and new on the content of the passed pointer.

well, alas. this 'c' style is almost ancient history. haven't used it for
ages. silly me! *hammers his head in the table*

well, at least lessons re-rememebered. that counts to something (hardly something,
though.. *sigh*)

sefip.

[Danny Kalev]

Sefi P wrote:
>
> Riddle solved - sorry, don't bother answering.
>
> it was simply a ** that was required, you can't pass * and "new" on it, you
> must pass pointer to this, and new on the content of the passed pointer.
>
> well, alas. this 'c' style is almost ancient history. haven't used it for
> ages. silly me! *hammers his head in the table*
>
> well, at least lessons re-rememebered. that counts to something (hardly something,
> though.. *sigh*)
>
> sefip.

Boy, I wish more questions on this forum were answered by their
posters:) It would save us some work...
The ** trick is a common idiom when passing a pointer to a function that
allocates the address for that pointer *and* binds storage to that
address (in other words, when you want the function to allocate and
assign an address). You can avoid the syntax mess by using *& instead:

void allocate(void *& p, int size)
{
p = new char[size]; //should work
}

Danny