Segmentation fault on accessing vector class member - c++

Question

I have a segmentation fault on this line in c++ :
vector<TemplateElement*> children = getChildren();
Class That inherits from abstract class TemplateElement
How to fix that ?
#include <iostream>
#include <ctime>
#include <cstdlib>
#include <vector>
#include "strings.h"
#include "aimlthat.h"
using namespace std;
using namespace aiml;
vector<string> That::elements() {
vector<TemplateElement*> children = getChildren();
vector<string> elements;
for (int i = 0, n = children.size(); i < n; i++) {
string text = children[i]->toString();
text = trim(text);
vector<string> vsText = split(text);
for(int j=0, m=vsText.size(); j<m; ++j) {
elements.push_back(vsText[j]);
}
}
return elements;
}
/****************************************************************************/
#include <iostream>
#include <ctime>
#include <cstdlib>
#include <vector>
#include <map>
#include "strings.h"
#include "aimltemplateelement.h"
#include "aimltext.h"
using namespace std;
using namespace aiml;
vector<TemplateElement*> TemplateElement::getChildren() {
return m_vtChildren;
}
/***************************************************************************/
#ifndef __AIMLTEMPLATEELEMENT_H__
#define __AIMLTEMPLATEELEMENT_H__
#include <iostream>
#include <ctime>
#include <cstdlib>
#include <vector>
#include <map>
#include "strings.h"
#include "aimlelement.h"
using namespace std;
using namespace aiml;
namespace aiml {
class TemplateElement : public AIMLElement {
public:
TemplateElement() {}
TemplateElement(vector<TemplateElement*> elements);
vector<TemplateElement*> getChildren();
virtual string toString() = 0;
private:
vector<TemplateElement*> m_vtChildren;
};
}
#endif
/***********************************************************************/
Here is the class That :
#ifndef __AIMLTHAT_H__
#define __AIMLTHAT_H__
#include <iostream>
#include <ctime>
#include <cstdlib>
#include "aimltemplateelement.h"
using namespace std;
namespace aiml {
class That : public TemplateElement {
public:
That() {}
vector<string> elements();
private:
};
}
#endif

Answer 1

You need to check for null pointer:
for (int i = 0, n = children.size(); i < n; i++) {
if(children[i]) //Be sure that children[i] is not null before dereferencing it
{
string text = children[i]->toString();
text = trim(text);
vector<string> vsText = split(text);
for(int j=0, m=vsText.size(); j<m; ++j) {
elements.push_back(vsText[j]);
}
}
}
[EDIT]
From your comment I see that all you need is initialize the pointer to That before using it, and btw don't forget to delete it when you finish:
That* that = new That();
that->elements();