Mobile Application Using Sencha Touch - JSON Request Generates Syntax Error - web-services

Question

I started playing a bit with Sencha Touch.
So I've built a really simple application based on one of the examples just to see how it goes.
Basically it creates a JSON Request which executes a Last.FM web service to get music events near the user's location.
Here's the JSON code:
var makeJSONPRequest = function() {
Ext.util.JSONP.request({
url: 'http://ws.audioscrobbler.com/2.0/',
params: {
method: 'geo.getEvents',
location: 'São+Paulo+-+SP',
format: 'json',
callback: 'callback',
api_key: 'b25b959554ed76058ac220b7b2e0a026'
},
callback: function(result) {
var events = result.data.events;
if (events) {
var html = tpl.applyTemplate(events);
Ext.getCmp('content').update(html);
}
else {
alert('There was an error retrieving the events.');
}
Ext.getCmp('status').setTitle('Events in Sao Paulo, SP');
}
})
};
But every time I try to run it, I get the following exception:
Uncaught SyntaxError: Unexpected token :
Anyone has a clue?

Answer 1

A couple of things. First of all the "Uncaught SyntaxError: Unexpected token :" means the browser javascript engine is complaining about a colon ":" that has been put in the wrong place.
The problem will most likely be in the returned JSON. Since whatever the server returns will be run though the eval("{JSON HTTP RESULT}") function in javascript, the most likely thing is that your problem is in there somewhere.
I've put your code on a little sencha test harness and found a couple of problems with it.
First: My browser was not too happy with the "squiggly ã" in location: 'São+Paulo+-+SP', so I had to change this to location: 'Sao+Paulo,+Brazil', which worked and returned the correct results from the audioscribbler API.
Second: I notice you added a callback: 'callback', line to your request parameters, which changes the nature of the HTTP result and returns the JSON as follows:
callback({ // a function call "callback(" gets added here
"events":{
"event":[
{
"id":"1713341",
"title":"Skank",
"artists":{
"artist":"Skank",
"headliner":"Skank"
},
// blah blah more stuff
"#attr":{
"location":"Sao Paulo, Brazil",
"page":"1",
"totalpages":"1",
"total":"2"
}
}
}) // the object gets wrapped with extra parenthesis here
Instead of doing that I think you should be using the callbackKey: 'callback' that comes with the example in http://dev.sencha.com/deploy/touch/examples/ajax/index.js.
Something like this for example:
Ext.util.JSONP.request({
url: 'http://ws.audioscrobbler.com/2.0/',
params: {
method: 'geo.getEvents',
location: 'Sao+Paulo,+Brazil',
format: 'json',
api_key: 'b25b959554ed76058ac220b7b2e0a026'
},
callbackKey: 'callback',
callback: function(result) {
// Output result to console (Firebug/Chrome/Safari)
console.log(result);
// Handle error logic
if (result.error) {
alert(result.error)
return;
}
// Continue your code
var events = result.data.events;
// ...
}
});
That worked for me so hopefully it'll work for you too. Cherio.