Question

I have this code:

var my = {};

(function () { 
    var self = this;
    this.sampleData = { };

    this.loadData = function() {
       $.getJSON('http://api.flickr.com/services/feeds/photos_public.gne?jsoncallback=?', 
          {tags: "cat", tagmode: "any", format: "json"},
          function(data){
             self.sampleData = data;
          }
       );
    };
}).apply(my);

my.loadData();
console.log(my.sampleData); // {}

The problem is my.sampleData not have anything.

Try this sample here: http://jsfiddle.net/r57ML/

Answer 1

The reason is that the getJSON call is asynchronous, so you’re looking for the data before it’s been returned. Instead, put your code using the data inside the callback, either directly or indirectly.

For instance, you can have your loadData call accept a callback:

var my = {};

(function () { 
    var self = this;
    this.sampleData = { };

    this.loadData = function(callback) {
       $.getJSON('http://api.flickr.com/services/feeds/photos_public.gne?jsoncallback=?', 
          {tags: "cat", tagmode: "any", format: "json"},
          function(data){
             self.sampleData = data;
             callback(); // <==== Call the callback
          }
       );
    };
}).apply(my);

my.loadData(function() { // <=== Pass in a callback
    console.log(my.sampleData); // Now the data is htere
});

---

Side note: Since your my object is a singleton, you can simplify that code a fair bit, no need for apply, this, or self, since your anonymous function is a closure over the context in which my is defined:

var my = {};

(function () { 
    my.sampleData = { };

    my.loadData = function(callback) {
       $.getJSON('http://api.flickr.com/services/feeds/photos_public.gne?jsoncallback=?', 
          {tags: "cat", tagmode: "any", format: "json"},
          function(data){
             my.sampleData = data;
             callback();
          }
       );
    };
})();

my.loadData(function() {
    console.log(my.sampleData); // Now the data is htere
});

Of course, if you’re using a constructor function or something instead (you weren’t in your quoted code, but…), then of course you might need the more complex structure.