传递指针到派生类，函数期望指向基类的指针？ [英] Passing pointer to derived class, to function that expects pointer to base class?

问题描述

好的。我不是很好的多态性在C + +，但我现在有一个问题。想象这些类：

OK. I'm not very good at polymorphism in C++, but I've a problem now. Imagine these classes:

class Parent {
public:
     Parent();
     virtual ~Parent();
};

class Child : public Parent
{
public:
     Child();
};

class Director
public:
     Director();
     void doStuff(Parent* p);
};


// Assume we have a instance of Director, and call the doStuff function here:
doStuff(new Child()); // Gives error

我得到错误

无法将参数1从Child *转换为Parent *

cannot convert parameter 1 from 'Child *' to 'Parent *'

是，为什么这不工作？
我需要做任何类型的铸造或什么，或什么是问题？

And my simple question is, WHY this doesn't work? Do I need to do any sort of casting or what, or what is the problem?

EDIT：
我把所有的文件在这里，因为他们是。
我认为问题在于我的包含，因为我真的不知道如何应该用#ifndef和这样做。请检查出来。

Director.h： http://pastebin.com/2uJqezju

Director.cpp： http://pastebin.com/SZ6cuBJC

IApp.h： http://pastebin.com/euCAwpnL

IApp.cpp： http://pastebin.com/JHDuQUhW

IScene：h： http://pastebin.com/cweH9G6p

IScene.cpp： http://pastebin.com/9epW0dRA

I put all my files here as they are. I think the problem lies in my inclusions, since I really dont have any idea of how it's supposed to be done with #ifndef and such. Please check them out.
Director.h: http://pastebin.com/2uJqezju
Director.cpp: http://pastebin.com/SZ6cuBJC
IApp.h: http://pastebin.com/euCAwpnL
IApp.cpp: http://pastebin.com/JHDuQUhW
IScene:h: http://pastebin.com/cweH9G6p
IScene.cpp: http://pastebin.com/9epW0dRA

然后我已创建了一些实例：

GameApp.h（继承EDGE :: IApp）： http： //pastebin.com/QbjbVqSi

GameApp.cpp： http：// pastebin。 com / sYJvmbeP

GameScene.h（继承EDGE :: IScene）： http：/ /pastebin.com/K1WYNvRf

GameScene.cpp： http://pastebin.com / uJx3FLBW

Then I have created some instances of it:
GameApp.h (inherits EDGE::IApp): http://pastebin.com/QbjbVqSi
GameApp.cpp: http://pastebin.com/sYJvmbeP
GameScene.h (inherits EDGE::IScene): http://pastebin.com/K1WYNvRf
GameScene.cpp: http://pastebin.com/uJx3FLBW

不要害怕检查它们，实际上每行中有10行代码他们。但问题是在GameApp.cpp中，我尝试创建一个GameScene的实例，并将其传递给Director-> createNewScene（IScene * scene）。

Don't be afraid to check them out, there are really like 10 lines of code in each of them. But the problem is in GameApp.cpp where I try to create an instance of GameScene, and pass it to the Director->createNewScene(IScene* scene).

推荐答案

Director.h：

Director.h:

class IScene;

应在命名空间内

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