Re: [Boost-users] Boost Graph: determining type of bundled property

On Wed, 7 Apr 2010, Trevor Harmon wrote:

Hi,

I wrote some Boost Graph code that uses a custom pointer type as the vertex:

adjacency_list >

I now need to expand the graph so that the Foo pointer is just one of several vertex properties. I assume bundled properties are the way to go:

http://www.boost.org/doc/libs/1_42_0/libs/graph/doc/bundles.html

I also need my vertices to be of different types (but all as children of a base type), such that my vertex bundles look something like this:

class BaseVertex { }; class EntryVertex : public BaseVertex { }; class ExitVertex : public BaseVertex { }; class FooVertex : public BaseVertex { Foo *foo; // ... other properties follow ... };

If you need that, you'll need to keep a (smart) pointer to the base class rather than a copy. I would recommend using boost::shared_ptr<BaseVertex> as the property type.

My goal is to be able to iterate through the vertices and perform different actions depending on the type of vertex. (e.g., if vertex type is EntryVertex do this, if vertex type is ExitVertex do that, etc.) However, I don't know how to determine a vertex's type. The bundles document mentions something about vertex_bundle_type<Graph>::type, but I have no idea how to use this. I couldn't find any code in the Boost examples that use it, either. Any tips to get me started?

That won't help you -- you need the dynamic type of the property, not the static type that would come from vertex_bundle_type. You need to just have a virtual member function (and/or a virtual destructor most likely) in BaseVertex then use typeid or dynamic_cast to find out the subclass stored in any given pointer.

Also, note that I've added an index property to my graph's edges, declared explicitly in the adjacency_list instantiation (as seen above). Would it make sense to convert this to a bundled property as well, or should I leave it as-is? (I don't think I'll ever need any edge properties other than the index.)

No, there's no reason to change that. You can mix bundled and non-bundled properties, and having an edge_index property with that name will make some algorithms easier to call. -- Jeremiah Willcock