How to check if values exist in a collection? (and other collection's stuff)

Hi,

I'm trying, in a loop, to check if a model (in fact, only its attribute "name" matters) exists in a collection, and then add it to the collection in the case where it doesn't exist. But, it seems that this part of code:

var match = _.find(myCities.models, function(myCity) {
                    return myCity == myCity;

Doesn't work properly...

This is my complete code:

var url = "http://myURL/myFile.php";
 
var xhr = Ti.Network.createHTTPClient({
    onload: function(e) {
        // this function is called when data is returned from the server and available for use
        // this.responseText holds the raw text return of the message (used for text/JSON)
        // this.responseXML holds any returned XML (including SOAP)
        // this.responseData holds any returned binary data
        Ti.API.debug(this.responseText);
 
        var myTable = JSON.parse(this.responseText);
 
        var myCities = Alloy.createCollection('cities');
 
        for(var i= 0; i < myTable.cities.length; i++)
            {   
                var myCity = myTable.cities[i].nom_commune;
 
                var match = _.find(myCities.models, function(myCity) {
                    return myCity == myCity;
                });
 
                if (match == 'undefined') {
                    var city = Alloy.createModel('cities', {name : myCity });         
                    city.save();
                    //alert('Le modèle ' + myCity + ' a bien été créé car il n\'existait pas...');
                }
                else{alert('Le modèle ' + myCity + ' n\'a pas été créé car il existe déjà');}
 
            }
 
        myCities.fetch({
            success: function(coll) {
                alert("You have " + coll.length +  " cities");
            },
            error: function() {
                alert("An error occurred");
            }
        });
 
    },
    onerror: function(e) {
        // this function is called when an error occurs, including a timeout
        Ti.API.debug(e.error);
        alert('error');
    },
    timeout:5000  /* in milliseconds */
});
xhr.open("POST", url);
xhr.send();  // request is actually sent with this statement
 
 
$.index.open();

Also, I create the collection each time the app starts and I don't know if this is a clean approach. Maybe should I check if the collection exists AND THEN create it in the case it doesn't, or instantiate it in the case it already has been created? In my loop, where a model is created, the model's name is also the same each time (var city), so is this a good way to do it or should I dynamically name each model?

Thanks for Help & advices!