Hi Tobias,
It seems as though the new changes have broken the AStar code I'm using.
I use:
neo4j-apoc 1.1-SNAPSHOT
neo4j-graph-algo 0.5-SNAPSHOT
AStar uses DefaultExpander and can no longer find it.
Here's an example of the code that worked until now.
DefaultExpander relExpander = new DefaultExpander();
relExpander.add(GISRelationshipTypes.BICYCLE_WAY, Direction.BOTH);
AStar sp = new AStar(graphDb, relExpander, costEval, estimateEval);
Path path = sp.findSinglePath(startNode, endNode);
The problem seems to be that AStar wants a RelationshipExpander but now I
can only create an Expansion<Relationship>.
Do you have any suggestions as to how to make this work again?
Regards,
Alex
On Wed, Jun 23, 2010 at 11:14 AM, Tobias Ivarsson <
tobias.ivars...@neotechnology.com> wrote:
> Hi Neo4j enthusiasts!
>
> Yesterday I committed an API that Mattias and I have been working on for a
> few days. It comes in the form of two new interfaces Expander and Expansion
> (in the org.neo4j.graphdb package), and four new methods in the Node
> interface (method names starting with "expand").
>
> The two main problems this API solves are:
> 1. Adds a clean way for getting related nodes from a source node.
> 2. Adds a type safe way for declaratively specifying any combination of
> RelationshipTypes and Directions to expand.
>
> This replaces what was actually an anti-pattern, but something we saw
> people
> doing a lot: using a depth-one traversal to get the nodes related to a
> node,
> without needing to bother with the Relationship interface. Example:
>
> // The most convenient way to write it in the past:
> Node source = ...
> Traverser traverser = source.traverse(
> Traverser.Order.DEPTH_FIRST,
> new StopAtDepth( 1 ),
> ReturnableEvaluator.ALL_BUT_START_NODE,
> TYPE_ONE, Direction.INCOMING,
> TYPE_TWO, Direction.OUTGOING);
> for (Node related : traverser) {
> doSomethingWith( related );
> }
>
> // The previously recommended (and bloated) way of doing it:
> Node source = ...
> for (Relationship rel : source.getRelationships( TYPE_ONE, TYPE_TWO )) {
> Node related;
> if (rel.isType(TYPE_ONE)) {
> related = rel.getStartNode();
> if (related.equals(source)) continue; // we only want INCOMING
> TYPE_ONE
> } else if (rel.isType(TYPE_TWO)) {
> related = rel.getEndNode();
> if (related.equals(source)) continue; // we only want OUTGOING
> TYPE_TWO
> } else {
> continue; // should never happen, but makes javac know that related
> is != null
> }
> doSomethingWith( related );
> }
>
> // With the new API:
> Node source = ...
> for (Node related : source.expand( TYPE_ONE, Direction.INCOMING )
> .add( TYPE_TWO, Direction.OUTGOING ).nodes()) {
> doSomethingWith( related );
> }
>
> The return type of the Node.expand(...)-methods are the new Expansion type,
> it defaults to expanding to Relationship, but the Expansion.nodes()-method
> makes it expand to Node. It also contains the add()-methods seen above for
> specifying RelationshipTypes to include in the expansion. The spelling of
> this method isn't perfectly decided yet, we are choosing between "add",
> "and" and "include", we want something that reads nicely in the code, but
> doesn't conflict with keywords in other JVM-languages ("and" is a keyword
> in
> Python, and I think "include" means something special in Ruby). There is
> also an Expansion.exlude(RelationshipType)-method for use together with the
> Node.expandAll().
>
> The Expansion is backed by the newly added companion interface Expander.
> This is an extension of RelationshipExpander that adds builder
> capabilities.
> It turns the functionality of the DefultExpander implementation class (now
> removed) into an interface in the API. RelationshipExpander is still around
> as a single method interface, which is useful for when you want to
> implement
> your own expansion logic.
>
> This API is added to trunk so that we can get feedback from everyone who
> use
> the snapshot builds of Neo4j, if the response to this API isn't positive,
> it
> will probably be removed before the release of 1.1, so please submit
> comments in this thread on what you think about this API.
>
> Happy Hacking,
> --
> Tobias Ivarsson <tobias.ivars...@neotechnology.com>
> Hacker, Neo Technology
> www.neotechnology.com
> Cellphone: +46 706 534857
> _______________________________________________
> Neo4j mailing list
> User@lists.neo4j.org
> https://lists.neo4j.org/mailman/listinfo/user
>
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