Difference between including a header file in .h and .cpp

['Mani]

Hi,

This is just a generic question, where i want to know what is the
difference in including a header file in a .h file and .cpp file.

I have a class called MyClass (MyClass.h & MyClass.cpp).
There is another class (OtherClass.h & OtherClass.cpp)
OtherClass.cpp has a forward declaration to a class called 'Calc' which
is in the namespace called 'Utils' like below:

Class Utils::Calc;

Now, i included the OtherClass.h file in my MyClass.h file and tried to
compile. I got the error:
something like: ' Calc is not a member of the namespace 'Utils'.

But including the OtherClass.h in MyClass.cpp file compiles fine.

Any Idea?

[Phlip]

Re: Difference between including a header file in .h and .cpp

Mani wrote:
[color=blue]
> Class Utils::Calc;[/color]

I don't know what that forward-declares. Prob'ly a class Utils containing a
nested class Calc.

You need this:

namespace Utils { class Calc; }

One of the points of namespaces is they never close. You can reopen and add
stuff to them at any time.

--
Phlip
http://www.greencheese.org/ZeekLand <-- NOT a blog!!!

['Mani]

Re: Difference between including a header file in .h and .cpp

Thanks Philip. Any idea why does the error come when i include it in
the header file, but not in the cpp file?

[Alan Johnson]

Re: Difference between including a header file in .h and .cpp

'Mani wrote:[color=blue]
> Hi,
>
> This is just a generic question, where i want to know what is the
> difference in including a header file in a .h file and .cpp file.
>
> I have a class called MyClass (MyClass.h & MyClass.cpp).
> There is another class (OtherClass.h & OtherClass.cpp)
> OtherClass.cpp has a forward declaration to a class called 'Calc' which
> is in the namespace called 'Utils' like below:
>
> Class Utils::Calc;
>
> Now, i included the OtherClass.h file in my MyClass.h file and tried to
> compile. I got the error:
> something like: ' Calc is not a member of the namespace 'Utils'.[/color]

Tried to compile what?
[color=blue]
>
> But including the OtherClass.h in MyClass.cpp file compiles fine.
>
> Any Idea?
>[/color]

It is hard to make any specific suggestions without seeing code. Can you
reduce your code to the smallest example that causes the error and post
that?

Alan

[gangs]

Re: Difference between including a header file in .h and .cpp

Can you give some more info on, Where have you declared the namespace
Utils?

gangs.