weird inheritence problem
June 15, 2002 05:58 PM
I have a class called CObject and a class called CPlayer. I want CPlayer to publibly inherit from CObject. So, in the class declaration, i do class CPlayer : public CObject; fairly simple. However, for some strange reason, I get the following error message..
error C2504: ''CObject'' : base class undefined
What does a class have to do to become "defined"?
p.s: yes, i included "CObject.h" in my "CPlayer.h"
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122
June 15, 2002 06:17 PM
Show us some of your code.
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June 15, 2002 06:23 PM
here is CObject.h
And here is CPlayer.h
#ifndef _Nicks_CObject#define _Nicks_CObject#include "CGame.h"class CSprite;class CObject{public: // Constructor / Destructor CObject(); virtual ~CObject() = 0; // Methods void SetSpritePointer(CSprite *ps) { pSprite = ps; } void Draw(RECT &rSource, RECT &rDestination); void SetWorldXPosition(int NewXPosition) { WorldXPosition = NewXPosition; } void SetWorldYPosition(int NewYPosition) { WorldYPosition = NewYPosition; } void SetLocalXPosition(int NewXPosition) { LocalXPosition = NewXPosition; } void SetLocalYPosition(int NewYPosition) { LocalYPosition = NewYPosition; } // Accessor int GetWorldX() { return WorldXPosition; } int GetWorldY() { return WorldYPosition; } int GetLocalX() { return LocalXPosition; } int GetLocalY() { return LocalYPosition; } int GetBoxX() { return rBoundingBox.top; } int GetBoxY() { return rBoundingBox.right; } RECT GetUpPic() { return rUpPic; } RECT GetLeftPic() { return rLeftPic; } RECT GetRightPic() { return rRightPic; } RECT GetDownPic() { return rDownPic; }protected: RECT rBoundingBox; int WorldXPosition; int WorldYPosition; int LocalXPosition; int LocalYPosition; CSprite *pSprite; RECT rLeftPic; RECT rRightPic; RECT rUpPic; RECT rDownPic;};#endif And here is CPlayer.h
#ifndef _CPlayer#define _CPlayer#include "CObject.h"#include "CGame.h"class CPlayer : public CObject{public: CPlayer() { SetRect(&rLeftPic, 199, 1, 230, 32); SetRect(&rRightPic, 67 ,1, 98, 32); SetRect(&rUpPic, 133, 1, 164, 32); SetRect(&rDownPic, 1, 1, 32, 32); SetRect(&rBoundingBox, 0, 0, 32, 32); } virtual ~CPlayer(){};private: char* Name;};#endif
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2,123
June 15, 2002 06:35 PM
CObject is an abstract class (it contains a pure virtual method - the destructor), meaning an instance of it can never be created, yet it has no virtual methods other than the destructor. Do you define those methods (Set_/Get_xx) somewhere? They should all be virtual so a derived class can inherit and override if necessary, or fall back on the base version.
June 15, 2002 06:43 PM
Hmm just made all the set/gets virtual, but it doesn''t seem to solve my problem. In case you were wondering why the ADT has no other virtuals, it''s because i haven''t finnished these classes yet, they are in a sort of BETA phase right now. Once I get what I have to work, i''ll add more (methods).
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324
June 17, 2002 04:10 AM
You cannot have pure virtual destructors.
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1,658
June 17, 2002 04:40 AM
quote: Original post by dalleboy
You cannot have pure virtual destructors.
Yes, you can. It''s usually the ''default'' choice when you want to make a class abstract, but do not have a function you want to make pure virtual.
However, you mustprovide an implementation for the destructor even though it is declared pure virtual.
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324
June 17, 2002 09:33 AM
quote: Original post by FrunyWell, I''ll be damned.
Yes, you can.
I thought I was so smart...I was always using protected constructors instead.
Thank you for enlightening me.
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June 18, 2002 09:02 AM
This is a very annoying problem, which I''m sure has a very easy solution. I Don''t know what else to try, so even if your not sure if it would work, post it anyways please. I''m desperate
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504
June 18, 2002 09:51 AM
The only reason that you will have this problem is that CObject is not visible to CPlayer for some reason. You quite possibly haven''t set-up your project configuration correctly, or maybe you''ve spelt something wrong. I also find CObject to be a dodgy class-name to use, knowing that MS have their own class with the same name.
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