Re: BGL properties question

From: Vladimir Prus (yg-boost-users_at_[hidden])
Date: 2003-03-28 01:16:28

Jeff Holle wrote:

> I would like to write a "generic" routine that prints the named vertex
> and edges properties.

Eeh... you must mean (name,value) pairs from graphvis graph?

> I can see in this code sibit (from graphviz.cpp) that the info that I
> want is present:
> 
>> vertex_label(const Vertex& u, const GraphvizDigraph& g) {
>>   boost::property_map<GraphvizDigraph,
>> boost::vertex_attribute_t>::const_type
>>     va = boost::get(boost::vertex_attribute, g);
>>   return (*(va[u].find("label"))).second;
>> }
> 
> It appears that va is a map<Vertex, map<string, "property value"> >

Yep.

> How would I write code that prints the names of the properites of a
> given vertex?  (It would involve iterating over the map whose find
> method is used in the above code segment).

In the code above, "va[u]" has the type std::map<std::string, std::string>.
You can just iterate over all elements of that map, printing keys: 

  boost::property_map<GraphvizDigraph,
    boost::vertex_attribute_t>::const_type
     va = boost::get(boost::vertex_attribute, g);
  const map<string, string>& m = va[u];
  for (const map<string, string>::const_iterator i = m.begin();
       i != m.end();
       ++i)
        std::cout << i->first << "\n";

Is it what you're after?

- Volodya