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C++ Activity.h is defined 2 times.

Velpus Captiosus

Well-Known Coder
I have a class Stack with a header file Stack.h which uses up another class with a header file Activity.h

I have a third class ActivityManager which uses up both the Stack and the Activity class.If I run the program and add in both Activity.h and Stack.h to the #include list I get a compilation error:Activity.h is defined 2 times in the script.How do I solve this issue?
The issue might have been encountered due to multiple inclusion of the header file Activity.h.

This is a common problem in C++ when a header file is included in multiple files, causing the same declarations.

You can include guards in your header files. Include guards are preprocessor directives that prevent a header file from being included multiple times in the same translation unit.
The solution suggested by @MilesWeb is the way to go. Write your activity.h like this

#ifndef ACTIVITY_H
#define ACTIVITY_H
// Actual contents of header file

This way when you include it a second time, it falls right through. This is how all include files in standard libraries work.

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