如何访问Boost图形库中的边缘属性

Question

I am trying to write a program that wraps the boost graph library so as to provide a convenient user interface. I am very new to boost (and stack overflow) but have spent quite a bit of time reading the boost documentation.

My problem is that whenever I go to get a property map for my edge properties, whether I am using bundled properties or internal properties, I get an error when ever call the get() function for an edge property saying that there is no function prototype that matches the given arguments. I have no difficulty when doing the same thing for my vertex properties. Moreover, the boost docs seem to also indicate that there is no get() function for edge properties. I think the problem may be in my constructor, which is designed to read graph information from a text file:

BGraph::BGraph()                                                           // constructor
{ 
    graph;          // is this how you would initialize the graph?
    //...input and initialization of vertices

    //...input of edge information

    auto e = add_edge(vertex1, vertex2, graph).first;                  // add the edge

    // this is the internal property version
    property_map<Graph, edge_weight_t>::type weightMap = get(edge_weight, graph);
                                    // ^^^^^ error here saying there is no such member
    weightMap[e] = inWeight;

    //graph[e].weight = inWeight;       this is the bundled version    // give the edge its weight

}

}

Here is my header file for the wrapper class:

#include <boost/config.hpp>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graph_traits.hpp>
#include <boost/graph/adjacency_iterator.hpp>
#include <boost/graph/dijkstra_shortest_paths.hpp>
#include <boost/graph/kruskal_min_spanning_tree.hpp>
#include <boost/graph/named_function_params.hpp>
#include <boost/graph/properties.hpp>
#include <boost/property_map/property_map.hpp>
#include <boost/graph/graphviz.hpp>

#include <string>
#include <vector>
#include <iostream>

using namespace std;
using namespace boost;

class BGraph
{
public:

    struct Edge_Properties                                      // property bundle for edges
    {
        string name;
        int weight = 1;
    };

    struct Vertex_Properties                                    // property bundle for vertices
    {
        string name;
        int distance;
        int pred;
    };

    // class member functions...

    typedef adjacency_list<vecS, vecS, bidirectionalS,          // graph type
        Vertex_Properties, property<edge_weight_t, int> > Graph;

 /*typedef adjacency_list<vecS, vecS, bidirectionalS,           // graph type
    Vertex_Properties, Edge_Properties> Graph;*/                // this is the bundled version

    typedef property_map<Graph, vertex_index_t>::type IdMap;
    typedef typename graph_traits<Graph>::vertex_descriptor vertex_descriptor;
private:
    Graph graph;                                                // the boost graph
}

I have similar problems in my function for dijkstra_shortest_paths :

dijkstra_shortest_paths(graph, findVertex(startVertex), 
    predecessor_map(get(&Vertex_Properties::pred, graph))
    .distance_map(get(&Vertex_Properties::distance, graph))
    .weight_map(/*get(&Edge_Properties::weight, graph)*/ get(edge_weight, graph)));

The specific error on the get function is as follows:

no instance of overloaded function "get" matches the argument list. argument types are: (boost:edge_weight_t, const BGraph::graph)

I feel like there is some overly simple solution, but I just have not been able to find it. I am using MS Visual Studio 2017 and boost version boost_1_67_0. I think the problem may have something to do with Visual Studio in particular because code almost identical to mine seems to work for other people. Thanks for your help.

Answer 1

It seems that your code should work for internal properties.

When you use bundled properties you need to specify PropertyTag for property_map as pointer to data member, in your case pointer to weight member of Edge_properties .

    property_map<Graph,int Edge_Properties::*>::type weightMap = 
                   get(&Edge_Properties::weight, graph);
                     //^^^^^
    auto e = add_edge(1, 2, graph).first;
    weightMap[e] = 10;
    graph[e].weight = 20;   

Here are examples of getting property map from bundled properties. You can easily adapt them to your needs.