How do I do forward referencing / declaration in C++ to avoid circular header file references?
I have the #ifndef guard in the header file, yet memory tells me I need this forward referencing thing - which i've used before >< but can't remember how.
+15
A:
You predeclare the class without including it. For example:
//#include "Foo.h" // including Foo.h causes circular reference
class Foo;
class Bar
{
...
};
antik
2008-10-08 17:32:04
Also to note in this case: class Bar cannot contain a class Foo, but it can have a pointer to a class Foo.
KPexEA
2008-10-08 18:12:08
Also note that the formal return type of functions can be of the forward declared type.
QBziZ
2008-10-08 18:14:17
A:
You won't get circular header files references if you have #ifndef guards. That's the point.
Forward referencing is used to avoid #include(ing) header files for objects you use only by pointer or reference. However, in this case you are not solving a circular reference problem, you're just practicing good design and decoupling the .h file from details it doesn't need to know.
Joe Schneider
2008-10-08 17:33:19
That's not accurate. forward referencing could replace the need for an #include and thus eliminating the need for an #include circle.
shoosh
2008-10-08 17:50:37
I agree that if you didn't have #ifndef guards, you might (sloppily) try to manage all your circular header dependencies by using forward declarations, however the OP said he DID have header guards.
Joe Schneider
2008-10-09 00:07:58
A:
I believe the correct term for what you are talking about is "forward declaration". "Forward referencing" would be a bit confusing.
Dima
2008-10-08 22:45:32