Is there some way i can create an object refering to a class which will be declared only AFTER the instance of the object??

For example, imagine this situation:
okay it works nice.

now imagine this:
the compiler returns error because the class y will be declared only after the object have been instanced.
it works well on c# but not on c++. is there some way to get this to work??
i know i can declare functions first and type the code after it is used, but i can't do that with classes, is there some way??
and, still, this is even more complicated because classes x and y will be in different headers (h. files). is there a way to make this work?? thanks.

Classes require knowledge of the size of each member encapsulated. This creates a problem that forward references alone cannot solve.

The solution is to use a pointer within at least one of the classes. eg.

thanks. now i've been able to create the objects, but still it doens't let me use any methods or proprietys or even the constructor of class y inside of class x (he says 'name_of_method' undeclared (first use this function)). is there some way around it??

Recall that the default access modifier with classes is private. Either relax the access modifiers used, or declare the classes to be friends of each other.

yes, but everything is declared as public.
forgeting about the cross reference, i'm now trying to make this work.

content of x.h:

content of y.h:

content of the .cpp file:

what happens is when i try to compile, dev c++ tells me request for member `ret' in `yyy', which is of non-class type `y*()()' and points this line var = yyy->ret();. which i tried to rewrite many ways like:
var = yyy.ret();
var = *yyy->ret();
and etc but none works.

and still, i have verified that when i the line y *yyy(); is executed, the y() constructor is not called.

what should i do in this case?? thanks.

Correct. You aren't calling the constructor with that syntax. The syntax you are quoting creates the prototype for a function. If you want to allocate a new instance of a class at runtime, the required syntax is:
...for the default constructor. If you want to call another constructor form which takes arguments, then use the following form:
The following statements:
...should generate a segmentation fault because a class instance has never been created. It appears that you need to study heapspace allocation with operator new(). One source covering this topic can be found at the following:

http://www.cplusplus.com/doc/tutorial/dynamic.html

thanks, that's a good link too, i'm still learning c and am doing it on my own.
but... still, this way:
i get the message invalid use of undefined type `struct y' pointing to the two lines above.

of course it works well if i include y.h before x.h, but my intention is that one of the classes in y.h will also reference a class from x.h.
heheh i'm beginning to assume either it's impossible, or there's something i'm just not being able to figure out.

well, let me describe better what really i intend to do for maybe there may be another way around it. what happens is that i'm creating a kinda large library, so instead of using a single .h file, i'm splitting it in differents files. each one of the files correponds to a topic of the library.
now, what happens is that many classes of each file will work with classes of other files.
now i'll have a lot of trouble if i have to worry about which class is declared first, and still, i'll never get it to work, since many classes will need many other classes the crossings will never get right and still, probably, two classes will work with (reference) each other like the example with x and y classes from my top post.

thanks for the help till now, got any ideas??

Correct. The forward reference only establishes (delays) the fact that y represents a user-defined type (class). What the compiler is complaining about here is the call to member function ret(). It has no advanced information about it without seeing the class declaration found in the header file, so it calls this error out to the user.
Creating an instance of y within the constructor to x means that an x object will create an y which in turn will create another x which creates yet another y, etc. The result of this seemingly infinite chain of events is that the stack (which is of finite size...) will be exceeded which will cause the application to crash during execution.
Again, I don't know what this is all meant to model, but as it is, you are describing the composition of tightly coupled classes. Does this really describe the relationship, or is the relationship better defined as one class refining/extending the behavior of the other? "is-a" relationships are better characterized by inheritance rather than composition.

well that was only an example, i don't really intend to create it in the constructor, i just put there so that the code i'd post here would be smaller. i thought about crashing, in fact i knew it would crash, for i tested something like that (the crossing reference on both constructors) on c# and it did crash (but it worked well when i trasnfered the object references to another method... but those are two different languages, it is sad i can't do that easily on c++), but that doesn't matter to me, i was just hoping it to compile, so that i would know how to implementate it in my library.


no, it's not that the case. but well... maybe i got kinda confused among the object orientation concepts, i'll think about this and maybe was trying to do the wrong way... if get to a conclusion, i post here again...

but... i was thinking about some stuff i've seen... for example, on .net i have the class frame (which is a box to insert objects inside) and i have the class panel (which is a different box but also used to insert objects inside). and then, i can insert a panel inside of a frame and a frame inside of a panel.
so i was thinking about insert an x object inside of an y and an y inside of a x. and i could make this exactly the way i posted above on .net.
another example is that a control inside the form (on .net or visual basic 6) has the property called Container... which returns the form he is inside.
but well.. i'll rethink this, and when i get to a conclusion, i'll post here, thanks.

Correct. The same will be true in C++; just realize that exercising the tight coupling within the constructor is problematic.