Calling parent's method

Question

I'm kinda newbie to all this c++ stuff, so this probably is a beginner's problem:

ListScreen.h

#ifndef _LISTSCREEN_H_
#define _LISTSCREEN_H_

#include "MAUI/Screen.h"

namespace CoolPlaces {
    namespace Views {
        using namespace MAUI;

        class ListScreen : public Screen {
            public:
                ListScreen();
                ~ListScreen();

                void keyPressEvent(int keyCode, int nativeCode) {}
                void keyReleaseEvent(int keyCode, int nativeCode) {}
                void pointerPressEvent(MAPoint2d point) {}
                void pointerReleaseEvent(MAPoint2d point) {}
                void pointerMoveEvent(MAPoint2d point) {}
                void show();
        };
    }
}

#endif    //_LISTSCREEN_H_

ListScreen.cpp

  #include "MAUI/Screen.h"
#include "ListScreen.h"

using namespace MAUI;
using namespace CoolPlaces::Views;

void ListScreen::show() {
    Screen::show();
};

I'm getting this error: D:\MosyncProjects\Views\ListScreen.cpp:22: Error: Unresolved symbol '__ZN4MAUI6Screen4showEv' line 22 in this Screen::show(); call (for purpose of this topic I removed some code). So what exactly am I doing wrong here?

Nothing wrong with your code. That's a linker error, not a compiler error. You need to link the library which defines `Screen::show()`. — Taylor Brandstetter, Dec 12 '13 at 18:27
Damn... So what can I do? Restart my IDE, restart my computer? Format disks? :D — Marek M., Dec 12 '13 at 18:28
Apparently you didn't provide an implementation for `Screen::show()` or didn't link the object file/library where it resides. — πάντα ῥεῖ, Dec 12 '13 at 18:29
_'Restart my IDE, restart my computer? Format disks?'_ Neither of these will correct your linker inputs ... — πάντα ῥεῖ, Dec 12 '13 at 18:30
@Taylor I linked library with definition for show method (header file, right?), and it still doesn't work. — Marek M., Dec 12 '13 at 18:31
Adding a header file to your project is not linking libraries. — drescherjm, Dec 12 '13 at 18:33
You're using a [reserved identifier](http://stackoverflow.com/questions/228783/what-are-the-rules-about-using-an-underscore-in-a-c-identifier). — chris, Dec 12 '13 at 18:34
@drescherjm actually I thought, that MoSync framework does that for me. — Marek M., Dec 12 '13 at 18:34
I assume you are using mingw? What is the IDE that you use? I can't help much on mingw but others will be able.. — drescherjm, Dec 12 '13 at 18:37
I'm pretty sure, that MoSync IDE (which is built on top of Eclipse) doesn't use mingw. I don't know which compiler it uses. — Marek M., Dec 12 '13 at 18:39
Probably not related but not that `_LIST_SCREEN_` is a name reserved to the C++ implementation (i.e., the compiler and the standard library): any name starting with an underscore followed by a capital letter is reserved and shall not be touched in any way unless explicit permission is granted (like for `__FILE__` etc.). — Dietmar Kühl, Dec 12 '13 at 18:41

score 4 · Accepted Answer · answered Dec 12 '13 at 18:38

You're including the header file, which tells that the function Screen::show() exists, but probably not linking the library, which has the implementation.

See this page: http://www.mosync.com/docs/sdk/cpp/guides/libs/working-with-mosync-libraries/index.html

Specifically:

As well as referencing the header files in your application code, you also need to specify the actual libraries that you want to use in the project's Build Settings (Project > Properties > MoSync Project > Build Settings):

It looks like maui.lib should contain the screen code.

Calling parent's method

1 Answers1