OOP organizing classes

[RezaA]

Hi, I have a problem in creating my main function. I have following classes:
1- SolarCalculation
2- TemperatureInputs
3- Params
In a way that I want to access some variables from an XML file to assign my variables in SolarCalculation class:

class TemperatureInputs
{
private:
	Params* pm;

public:
	TemperatureInputs(std::string XmlFilename);
	~TemperatureInputs(){};
	Params* getPM(){ return pm; }
};

class Params
{
public:
int get_starttime()
        {
	std::pair<std::string, std::string> stringpair = Temporal_Domain[0]->GetAttributes(0);
	this->EatDoubleQuote(stringpair.second);
	return atoi(stringpair.second.c_str());
        } 

private:
std::vector<Node*> Temporal_Domain;

};

class SolarCalculation
{
public:
	
	SolarCalculation(TemperatureInputs* input);

	SolarCalculation() {};
	~SolarCalculation() {};

	void SolarConst();
};

SolarCalculation::SolarCalculation(TemperatureInputs* input)
{
	Params* pm = inp->getPM();
	startYear = pm->get_starttime();
}

void SolarCalculation::SolarConst()
{
	/*  convert to radians  */
	double lat_deg = startYear;

}

/* In the main, I want to get access the startYear using the SolarConst() function but I have a problem.  */

int main()
{
	SolarCalculation SolarCal;
	SolarCal.SolarConst();
}

Would you guide me about the general procedure for such issues, I have lots of variables I have to read in from the XML file in this way, but the constructor and/or the functions are not well organized!!

Thanks.

[gunnerfunner]

You also have a data-type Node it seems (line 23)

I want to access some variables from an XML file to assign my variables in SolarCalculation class

To read in data from the file you can try overloading the extraction operator (>>) for the SolarCalculation class to read the relevant data directly into SolarCalculation objects and then store these objects in a container such as std::vector<SolarCalculation> for further use by the rest of your program. However your exact requirements will be determined by the pattern of the data file and the corresponding class

[raschupkin]

Writing into xml file is easy: just write tags and values.
To read from xml you need a xml-parser library. Most parsers are either DOM or SAX. DOM occupy more memory and slower for big files, but easier to use.