Most of time we used classes and sorts the collection of objects on different member variables. In these scenarios we have to write different-different Functor with respect to the classes. The following code provides a generic Functor which can be used with any class and can be used easily.
#include<iostream>
#include<vector>
#include <functional>
#include <algorithm>
template <typename T1,typename T2> class Functor
{
public:
Functor( T1 T2::* t):memPointer(t) {}
bool operator() ( const T2 & obj1, const T2 & obj )
{
return obj1.*memPointer < (obj.*memPointer);
}
T1 T2::* memPointer;
};
struct ABC{
double x;
double y;
};
int main()
{
std::vector<ABC> vec;
ABC ab;
ab.x = 9;
ab.y = 89;
vec.push_back(ab);
ab.x = 10;
ab.y = 10;
vec.push_back(ab);
ab.x = 5;
ab.y = 100;
vec.push_back(ab);
Functor<double,ABC> bb(&ABC::x);
std::sort(vec.begin(), vec.end(), bb);
std::vector<ABC>::iterator itr = vec.begin();
for (itr = vec.begin(); itr != vec.end(); ++itr)
std::cout << itr->x <<std::endl;
std::cout <<”——————–”<<std::endl;
Functor<double,ABC> b2(&ABC::y);
std::sort(vec.begin(), vec.end(), b2);
for (itr = vec.begin(); itr != vec.end(); ++itr)
std::cout << itr->y <<std::endl;
return 0;
}
Out put:
Sorted on member variable x
9
10
100
Sorted on member variable y
10
10
89