[英]How can I solve this error in Printing Nodes and Edges Boost Graph Library?
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'我已经编写了以下 function 来打印出我的图形节点和边的大小,但是这个 function 不起作用,错误是:错误:非静态数据成员“MyGraph”的使用无效
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";
}
MyGraphBuilder::MyGraph
names a type. MyGraphBuilder::MyGraph
命名一个类型。 If you want to pass a parameter and use it , you'll have to name it:如果你想传递一个参数并使用它,你必须命名它:
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
:为了提高效率,您可以通过引用传递(在这种情况下,
const&
将起作用,因为您没有修改图形)以避免复制整个图形只是为了调用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.请注意我是如何标记成员 function
const
的,因为我们可以。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.或者,您可以将其标记为
static
成员 function 因为您正在传递图表,无论如何,我们根本不使用MyGraphBuilder
的成员。 Honestly, that feels likeprintGraph
should not be a member of that class in the first place.老实说,感觉
printGraph
不应该是 class 的成员。
Bonus:奖金:
Be advised that there is a print_graph
utility in boost/graph/graph_utility.hpp
already.请注意,在
boost/graph/graph_utility.hpp
已经有一个print_graph
实用程序。 How to make it print the properties you want depends on the actual type of your graph, so here's a pretty random example:如何让它打印你想要的属性取决于你的图形的实际类型,所以这是一个非常随机的例子:
#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:印刷:
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
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