#include <iostream>
#include <TRandom3.h>
#include <TFile.h>
#include <TTree.h>

/*
 Simple class holding a single parameter
 */
class subDataClass{
	public:
	subDataClass();
	void setParam(int);
private:
	int param;
	ClassDef(subDataClass,1);
};

/*
 Class holding a variable length array of subDataClass
 The array length is given by nVar
 */
class mainDataClass{
public:
	mainDataClass();
	mainDataClass(int nVar);
	~mainDataClass();
	void setParam(int);
private:
	int nVar;
	subDataClass* data;//[nVar]
	ClassDef(mainDataClass,1);
};


ClassImp(subDataClass);
ClassImp(mainDataClass);

/*
 Implementation of subDataClass
 */
subDataClass::subDataClass(){
	param=0;
}

void subDataClass::setParam(int param_){
	param=param_;
}

/*
 Implementation of main data class
 */
mainDataClass::mainDataClass(){
	nVar=0;
	data=NULL;
}

mainDataClass::mainDataClass(int nVar_){
	nVar=nVar_;
	data = new subDataClass[nVar];
}

mainDataClass::~mainDataClass(){
	if(data!=NULL){
		delete [] data;
		data=NULL;
	}
}
	
void mainDataClass::setParam(int a){
	for (int i=0; i<nVar; i++)
		data[i].setParam(a);
}

/*
 Main function to test classes
 */
void go(){
	
	TFile *outfile = new TFile("testout.root","recreate");
	TTree *outTree = new TTree("tree" ,"test tree");

	mainDataClass *gr = new mainDataClass(3);
	outTree->Branch("mainDataClass", &gr);
	
	for (int i=0; i<5; i++){
		gr->setParam(100);
		outTree->Fill();
	}
	outTree->Scan("data[1].param");
	outTree->Write();
	outfile->Close();
}