error: expected class-name before { token

This is a discussion on error: expected class-name before { token within the C++ Programming forums, part of the General Programming Boards category; Really don't understand why I get the compile error. I put a big arrow on the line this error appeared ...

  1. #1
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    error: expected class-name before { token

    Really don't understand why I get the compile error. I put a big arrow on the line this error appeared on. I've tried rearranging the order of the includes and stuff like that, but even if that worked I wouldn't understand why.

    Code:
    ----MAIN.cpp----------------
    #include <G3D/G3DAll.h>
    #include <GLG3D/GLG3D.h>
    
    #include "App.h"
    #include "Demo.h"
    
    
    int main(int argc, char** argv) 
    {
    	GAppSettings settings;
    	settings.window.width = 800;
    	settings.window.height = 600;
    
    	App app(settings);
    	app.setDebugMode(true); 
    	app.debugController.setActive(true);
    
    	app.run();
    	return 0;
    }
    
    -----DEMO.h-------------------
    
    #ifndef Demo_H
    #define Demo_H
    
    #include <G3D/G3DAll.h>
    #include <GLG3D/GLG3D.h>
    #include "App.h"
    
    class Demo : GApplet {                   <<<<-----------------------------Here's the ERROR  
     public:
      Demo(App* app) : app(app) {}
        void doGraphics();
    
     private:
        const App* app;
    };
    
    #endif
    
    
    ------APP.h------------------
    #ifndef App_H
    #define App_H
    
    #include <G3D/G3DAll.h>
    #include <GLG3D/GLG3D.h>
    #include "Demo.h"
    
    class App : public GApp {
     public:
      App(const GApp::Settings& settings): GApp(settings) {} 
    		void main();
    };
    
    #endif
    
    -------APP.cpp---------------
    
    #include "App.h"
    
    void App::main()
    {
    	Demo(this).run(); 
    }
    
    ------DEMO.CPP-------------
    
    #include "Demo.h"
    
    void Demo::doGraphics() {
      app->renderDevice->clear(true, true, true);
      app->renderDevice->setProjectionAndCameraMatrix(app->debugCamera);
      Draw::axes(Vector3(0,4,0),app->renderDevice);
    }
    Last edited by keira; 12-21-2007 at 12:05 AM.

  2. #2
    and the hat of sweating
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    Is GApplet defined in one of those header files?
    You should also be explicit about what kind of inheritance you want (i.e. public, protected or private), otherwise people might just think you forgot to add the keyword...

  3. #3
    and the hat of wrongness Salem's Avatar
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    Spelling perhaps?

    I see 'App' and 'GApp', but no 'GApplet'
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  4. #4
    C++まいる!Cをこわせ! Elysia's Avatar
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    You're mixing spaces and tabs - bad. Use ONE and stick with it. I recommend tabs.
    And come on - one space for indentation - that's kind of cheap, isn't it? Use AT LEAST 4 spaces if you're going for spaces.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  5. #5
    Cat without Hat CornedBee's Avatar
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    You have a recursive include between app.h and demo.h. There's no reason for app.h to include demo.h.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
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  6. #6
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    yeah I thought recursive include or something like that so I've been messing around with the include statements... Nothing works though.

    The line in question should be "class Demo : public GApplet {"

    I just don't understand this error.

  7. #7
    C++まいる!Cをこわせ! Elysia's Avatar
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    If you have referencing headers, then you must use a forward declaration, like
    Code:
    class GApplet;
    ...before the code that uses it. Then include the proper header file inside the .cpp file.
    It's difficult to test this because many of the required classes are missing, so it won't compile properly.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  8. #8
    C++ Witch laserlight's Avatar
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    Instead of including App.h in Demo.h, use a forward declaration:
    Code:
    class App;
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  9. #9
    Cat without Hat CornedBee's Avatar
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    I still don't see anything in App.h that references Demo.h's contents in any way.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

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