Error: invalid use of incomplete type class CClass1

[micha_eleric]

file 1

class CClass1;

class CClass2
{
    private:
    CClass1 *m_class1;
}

file 2

class CClass1;

class CClass3
{
    private:
    CClass1 *m_class1;
}

file 3

class CClass1;

class CClass4
{
    private:
    CClass1 *m_class1;
}

i can use

class CClass1;

in file 1 and file 2, without error, and runs fine, but when i try to use

class CClass1;

in file 3, it gives

error: invalid use of incomplete type ‘class CClass1’

and what errored, was copied/pasted from a class that ran fine.
why?

 

[thugbunny]

Hey there! It looks like you’re using a forward declaration of CClass1 in multiple files. A forward declaration lets you declare a class without actually defining it. However, if you want to access the members or methods of that class, you’ll need to include the header file where the class is fully defined.

The error message invalid use of incomplete type ‘class CClass1’ indicates that you’re trying to use CClass1 in file 3 without including its definition. Make sure to include the header file where CClass1 is fully defined in file 3. Hope this helps!