问题
I have written the following function to print out just the size of My Graph Nodes and Edges, but this function didn't work, the Error was : error: invalid use of non-static data member 'MyGraph'
typedef adjacency_list < vecS, vecS, directedS, property < vertex_name_t, idType >, property < edge_weight_t, double > > graph_t;
class MyGraphBuilder{
private:
graph_t MyGraph;
}
void MyGraphBuilder::printGraph(MyGraphBuilder::MyGraph){
unsigned long long NodesCount = num_vertices(MyGraphBuilder::MyGraph);
cout<<"Number of Vertices is :\t"<<NodesCount<<"\n";
unsigned long long EdgesCount = num_edges(MyGraphBuilder::MyGraph);
cout<<"Number of Vertices is :\t"<<EdgesCount<<"\n";
}
回答1:
MyGraphBuilder::MyGraph
names a type. If you want to pass a parameter and use it, you'll have to name it:
void MyGraphBuilder::printGraph(MyGraphBuilder::MyGraph g) {
cout << "Number of Vertices is :\t" << num_vertices(g) << "\n";
cout << "Number of Edges is :\t" << num_edges(g) << "\n";
}
To be more efficient you can pass by reference (in this case, const&
will work because you're not modifying the graph) to avoid copying the entire graph just for the call to printGraph
:
void MyGraphBuilder::printGraph(MyGraphBuilder::MyGraph const& g) const {
cout << "Number of Vertices is :\t" << num_vertices(g) << "\n";
cout << "Number of Edges is :\t" << num_edges(g) << "\n";
}
Note how I marked the member function
const
as well, because we can.Alternatively you can mark is as a
static
member function because you're passing the graph in, anyways, we are not using members ofMyGraphBuilder
at all. Honestly, that feels likeprintGraph
should not be a member of that class in the first place.
Bonus:
Be advised that there is a print_graph
utility in boost/graph/graph_utility.hpp
already. How to make it print the properties you want depends on the actual type of your graph, so here's a pretty random example:
Live On Coliru
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graph_utility.hpp>
#include <iostream>
#include <random>
using boost::make_iterator_range;
struct VertexProperties { std::string name; };
struct EdgeProperties { double weight = 0; };
struct MyGraphBuilder {
using MyGraph = boost::adjacency_list<boost::vecS, boost::vecS, boost::directedS, VertexProperties, EdgeProperties>;
MyGraphBuilder(MyGraph& g) : _target(g) {}
void generate();
private:
MyGraph& _target;
};
void printGraph(MyGraphBuilder::MyGraph const& g) {
std::cout << "Number of Vertices is:" << num_vertices(g) << "\n";
std::cout << "Number of Edges is:" << num_edges(g) << "\n";
boost::print_graph(g, boost::get(&VertexProperties::name, g), std::cout);
// to print with edge weights:
for (auto v : make_iterator_range(vertices(g))) {
for (auto oe : make_iterator_range(out_edges(v, g))) {
std::cout << "Edge " << oe << " weight " << g[oe].weight << "\n";
}
}
}
#include <boost/graph/random.hpp>
void MyGraphBuilder::generate() {
std::mt19937 prng { 42 }; // fixed random seed
boost::generate_random_graph(_target, 5, 5, prng);
_target[0].name = "one";
_target[1].name = "two";
_target[2].name = "three";
_target[3].name = "four";
_target[4].name = "five";
for (auto e : boost::make_iterator_range(edges(_target))) {
_target[e].weight = std::uniform_real_distribution<>(1.0, 10.0)(prng);
}
}
int main() {
MyGraphBuilder::MyGraph g;
{
MyGraphBuilder builder{g};
builder.generate();
}
printGraph(g);
}
Printing:
Number of Vertices is:5
Number of Edges is:5
one -->
two --> four
three --> one one
four --> three
five --> one
Edge (1,3) weight 1.52275
Edge (2,0) weight 8.79559
Edge (2,0) weight 6.41004
Edge (3,2) weight 7.37265
Edge (4,0) weight 1.18526
来源:https://stackoverflow.com/questions/58974799/how-can-i-solve-this-error-in-printing-nodes-and-edges-boost-graph-library