Gremlin Scala Neo4j: Search for node, add new node and edge between - gremlin

Question

I am unable to find a node via a key and then add a new node and an edge between them. with the movie nodes already in graph, i use:
case class GraphBuilder(movieId: Int, personId: Int)
//
val Ident = Key[String]("personId")
val ItemId = Key[String]("movieId")
//
def applyToGraph(it: GraphBuilder): Unit = {
val thisPerson = graph + ("Person", Ident -> it.personId.asInstanceOf[String])
val movies = graph.V.hasLabel("Movie").has(ItemId, it.movieId)
movies.headOption match {
case Some(v) =>
v --- "likedBy" --> thisPerson // tested with println("yay" + v)
case None => println("youre a failure")
}
graph.tx.commit()
}
But each time I run this programmatically, it correctly adds the person to the graph via thisPerson val, correctly finds the movie vertex based on the movieId, but does not create the "likedBy" edge. I have also tried without pattern matching on the option but that does not work either.
What method is best to find node, add node, add edge between added and found?

Answer 1

I'm a bit confused by the syntax in your snippet, but since you have to have the identifiers for both vertices, the following query should do the trick:
g.V().has("Movie", "movieId", movieId).as("m").
V().has("Person", "personId", personId).
addE("likedBy").to("m").iterate()
If the person vertex doesn't exist yet:
g.V().has("Movie", "movieId", movieId).as("m").
addV("Person").property("personId", personId).
addE("likedBy").to("m").iterate()
And if you don't know whether the person vertex already exists or not:
g.V().has("Movie", "movieId", movieId).as("m").
coalesce(
V().has("Person", "personId", personId)
addV("Person").property("personId", personId)).
addE("likedBy").to("m").iterate()