Question

I’m trying to user node-proxy to auto-magically read/write databases and I can’t figure a solution.
Here is the code:

var Proxy = typeof Proxy !== "undefined" ? Proxy : require("node-proxy");  
var db = require('mongojs').connect('testdb',['colldb']);

function itemHandler(objid) {

  var objid=objid;


  return Proxy.create({ 
    get: function(receiver, name) {
        var name = name;
        var hmmm;

//Problem Area!
          db.colldb.findOne({"_id": db.ObjectId(objid)},function(err,doc){
            hmmm = doc[name];
          });

//Hmmm will obviously be undefined  
        return hmmm;
      }
    , set: function(receiver, name, val) {
        // this can be async and I don't care :)
      }
  });
}


var test = itemHandler('4efc0c698b7e904ee982547f');
console.log(test.test);

process.exit(0);

Normally I would be ok with the call backs but I’m unsure how to make that work with node-proxy return on the ‘get’ method.
I’m looking for any solution to this that I can return the proxy data based on the database result.

Thanks

Answer 1

First, nothing is going to work in this example because of the process.exit(0) line at the end. The program will terminate before the asynchronous functions complete.

Second, you cannot return a value from the results of an asynchronous function. This is a fundamental concept. I am not familiar with mongojs, but perhaps the following will work (I believe it would with Mongoose).

...
return Proxy.create({ 
get: function(receiver) {
    return db.colldb.findOne({"_id": db.ObjectId(objid)});
});
...

Then the last lines would be something like:

itemHandler('4efc0c698b7e904ee982547f').exec(function (err, doc){
  console.log(doc.test);
});

Alternatively, you may be able to return a Promise/Future. Something like:

...
return Proxy.create({ 
get: function(receiver, name) {
    var name = name
      , promise = new Promise(); // You'll need a library for this, of course.
    db.colldb.findOne({"_id": db.ObjectId(objid)}, function (err, doc){
      promise.complete(doc[name]);
    });
    return promise;
});
...