I have get the problem when compiling my code - undefined reference to `Rectangle<int>::Rectangle()'

Question

**header file **

#ifndef WIKI_H
#define WIKI_H

template<class T>

class Rectangle
{

private:

T length;
T breadth;

void printarea();

public:

Rectangle();
};

#endif

**source file**

#include "Wiki.h"
#include <iostream>

using namespace std;

template<class T>
void Rectangle<T>::printarea()
{

cout<< "Area = " << length*breadth <<endl;
}

template <class T>
Rectangle<T>::Rectangle()
{

cout<< "Enter Length" <<endl;
cin>> length;
cout<< "Enter Breadth" <<endl;
cin>> breadth;

printarea();
}

**main file**

#include <iostream>
#include "Wiki.h"

using namespace std;

int main()
{

Rectangle<int>X;

return 0;
}

Answer 1

Template classes have to be defined inline.
Which basically means copy pasta your definitions from the .cpp file to the .h ( Below the class ) and then add std:: where necessary since using namespace std; in a .h is to be avoided. ( Can still use it in local scope though )

Also you may want to use a space at Rectangle<int> <space> X.