How do I retrieve non blank objects from a Cypher Query in Node.js

Question

Given a node, I want to query for any incoming relationships for that node and return nodes that have that relationship. I am modifying Node Neoj4 Template

I am expecting to get back an array of nodes, create objects for each element and then reference the nodes properties. Instead I get back empty objects. I do, however get the correct number of nodes for the query (i.e. 2 inbound relationships, returns 2 elements).

I have run the query in the cypher shell and I get the results that I expect. I am using Neo4j 1.9.2

About the Graph: I have a genealogy graph consisting of 8 People nodes and 2 relationship types: INHERITS_X, INHERITS_Y. This refers to the the chromosomes that determine sex. For example, if I have two children then I have 2 incoming relationships; my son INHERITS_Y and my daughter INHERITS_X.

Any help appreciated.

Thanks,

Here is where the query function (getInbound) is called:

exports.show = function (req, res, next) {
    Person.get(req.params.id, function (err, person) {
      if (err) return next(err);
      person.getInbound(function (err, inbound) {
      res.render('person', {
              person: person
      })
      })
})

};

And the getInbound function:

Person.prototype.getInbound = function(callback) {
        var query = ['START p=node({ID})',
                     'MATCH p <-[:INHERITS_Y|INHERITS_X]- m',
                     'RETURN m'
        ].join('\n');

        var params = {
          ID: this.id,
          NAME: this.name
        };

        console.log("In getInbound function");
        console.log("this.name is  ",this.name);
        var in_nodes = [];

       db.query(query, params, function (err, results) {
               console.log("Error from the query ",err);
            if (err) return callback(err);
            console.log("Number of elements in array returned from query: ", results.length);
            for (var i=0; i< results.length; i++) {
                    console.log(" In the for loop, var i = ",i);
               var in_node = new Person(results[i]);
               console.log("New Person object created  from array element ", in_node);
               in_nodes.push(in_node);
              }
             callback(null, in_nodes);
         });

};

Output from running the code:

Express server listening on port 5000 
GET /persons 304 77ms 
IN getInbound - this.name is  Eddie Dickey 

Error from the query  null

results length returned from query:  2  

In the for loop, var i =  0 
Creating a new Person object form each element of array returned from query { _node: { m: { db: [Object], _request: [Object], _data: [Object] } } }  

In the for loop, var i =  1 
Creating a new Person object form each element of array returned from query { _node: { m: { db: [Object], _request: [Object], _data: [Object] } } } GET /persons/0 200 21ms - 602b

And the Person constructor:

var Person = module.exports = function Person(_node) {
    // all we'll really store is the node; the rest of our properties will be
    // derivable or just pass-through properties (see below).

    this._node = _node;
}

Answer 1

Cypher query results are never just an array of nodes -- they're an array of results, where a "result" is a dictionary of variable name to the corresponding (node/rel/path/etc.) object.

So in your example, your Cypher query says RETURN m, so in your for loop, you need to access results[i]['m'], not just results[i].

Hope this helps.