Question

I am newbie in OOP and I try to build an object using ajax request. What I need is to get ‘responseArray’ in JSON format and than work on it.

function adres(adres) {

this.adres_string = adres;
var self = this
$.ajax({
    type: 'POST',
    url: "http://nominatim.openstreetmap.org/search?q="+adres+"&format=json&polygon=0&addressdetails=0",
    success: function(data) {
        self.responseArray = eval('(' + data + ')')

    }

})


//Method returning point coordinates in EPSG:4326 system
this.getLonLat = function() {

    var lonlat = new OpenLayers.LonLat(this.responseArray.lon, this.responseArray.lat);
    return lonlat;

}
}

The problem starts when in appilcation code I write:

var adr = new adres('Zimna 3, Warszawa');
adr.getLonLat();

This returns nothing as there is no time get the response from the server.
How to write it properly in the best way? I’ve read about when().then() method in jQuery. This may be OK for me. I just want to get know best practise

Answer 1

This is how AJAX works (notice the A-synchronous part). You are right, the moment you call adr.getLonLat() response did not yet came back. This is the design I would suggest: just pass callback function reference to adres constructor:

function adres(adres, callbackFun) {
  //...
  success: function(data) {
    var responseArray = eval('(' + data + ')')
    var lonlat = new OpenLayers.LonLat(responseArray[i].lon, responseArray[i].lat);
    callbackFun(lonlat)
}

and call it like this:

adres('Zimna 3, Warszawa', function(lonlat) {
  //...
})

Few remarks:

• adres is now basically a function, you don’t need an object here.

• do not use eval to parse JSON, use JSON object.

• Are you sure you can POST to http://nominatim.openstreetmap.org? You might hit the same origin policy problem

• where is the i variable coming from in responseArray[i]?