How to get iterator over only the members of a class inside a container in C++

In C ++, I wonder if there is a way to get an iterator that only traverses a specific member of a class when it is contained in a container.

The situation is as follows.

class Edge : public std::pair<int, int>
private:
int length;
public:
int weight;
Edge::Edge(int v1, int v2): std::pair<int, int>(v1, v2)


int main()
enum nodes A, B, C, D, E ;
const int num_nodes = 5;
vector<Edge> edge_vec = Edge(A, C), Edge(C, D), Edge(B, D), Edge(B, E) ;
int weights = 1, 2, 7, 3 ; // I don't like this part.
graph_t g(edge_vec.begin(), edge_vec.end(), weights, num_nodes);



The definition of graph_t is graph_t (,, Iterable,);.

Therefore, any Iterable can be assigned as the third argument.

graph_t

graph_t (,, Iterable,);

The problem is this.

I do not want to use a separate int weights array because Edge class already have weight.

So I want to get an Iterator that can be initialized as follows and then traversed.

int weights

weight

edge_vec[0].weight = 1;
edge_vec[1].weight = 2;
edge_vec[2].weight = 7;
edge_vec[3].weight = 3;


In this case, weight is updated frequently, so I want to access it with a pointer instead of a copy in a separate data structure.

What is the most effective and elegant way to handle this?

weight

1 Answer
1

#include <boost/iterator/transform_iterator.hpp>
// ...
boost::transform_iterator wbegin(edge_vec.begin(), std::mem_fn(&Edge::weight));
boost::transform_iterator wend(edge_vec.end(), std::mem_fn(&Edge::weight));


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