Pointer to class

[j3lps]

Hi all, I'm trying to get a simple program to work, but have got stuck very early on, and can't figure out why.

So I have a header file which define 2 classes:

class CPlant
{
public:
	CPlant();
	CRoot* root_system;  // error C2143
	float stM;
	CPlant* PP;
};

class CRoot
{
public:
	CRoot(CPlant* PP);
	float get_C_conc(float vm);
	CPlant* PPlant;
};

And then the body which simply creates an object:

int main(){
	CPlant MyObject;
	return 0;
}

CPlant::CPlant() 
{
	PP = this; 
	root_system = new CRoot(PP); 	
}

CRoot::CRoot(CPlant* PP)
{
	PPlant = PP;
}

However it won't compile as it produces errorC2143: syntax error : missing ';' before '*' where I have marked above. Can anyone tell me what's wrong with this?
Many thanks. J.

[demosthenes2k8]

The problem is that, up until that line, there's been no mention of CRoot. Try:

class CRoot;

class CPlant
{
public:
	CPlant();
	CRoot* root_system;
	float stM;
	CPlant* PP;
};

class CRoot
{
public:
	CRoot(CPlant* PP);
	float get_C_conc(float vm);
	CPlant* PPlant;
};

[j3lps]

Thanks - that works. How weird - I assumed a header file was not read in order... Cheers.

[demosthenes2k8]

Welcome, I was excited that I knew the answer! Welcome to http://en.wikipedia.org/wiki/Dependency_hell you have to make sure that there's actually SOME mention of that class before you use it.

[firedraco]

Basically all #include does is copy/paste the file into wherever you have the include.