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Can you define two classes on the same source file?

Dec 31, 2018 at 10:10pm
Tduck (67)
I have an issue with a program I am creating that wants to use one object as a parameter. When I had first wrote the program, I ended up with huge errors regarding cyclic dependency, but now I don't know what the syntax would be to define two classes on a single source file. I need an implementation file as well, which is generally where errors get generated like class not defined. 

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#ifndef //ifndef what?  class1,class2?  
#define //define what?  


class CLASS1
{
    void useOtherClass(class2 object1);
};

class CLASS2
{
    void useOtherClass(class1 object2);
};

#endif



Edit, additionally, if I must stick to multiple header files, what is causing classes to be undeclared here? 

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#ifndef CLASS1_H
#define CLASS1_H

#include"CLASS2.h"

class CLASS1
{
    void useOtherClass(CLASS2 object1);
};


#endif 



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#ifndef CLASS2_H
#define CLASS2_H

#include"CLASS1.h"

class CLASS2
{
    void useOtherClass(CLASS1 object2);
};


#endif
Last edited on Dec 31, 2018 at 10:18pm
Dec 31, 2018 at 10:28pm
jonnin (11477)
look up an example of 'forward declaration'

Dec 31, 2018 at 10:30pm
dhayden (5799)
You just need a forward declaration for each class:
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#ifndef CLASS1_H
#define CLASS1_H

#include"CLASS2.h"
class CLASS2;

class CLASS1
{
    void useOtherClass(CLASS2 object1);
};


#endif

And

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#ifndef CLASS2_H
#define CLASS2_H

#include"CLASS1.h"
class CLASS1;

class CLASS2
{
    void useOtherClass(CLASS1 object2);
};

#endif
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