How to handle asynchronous requests to rest apis in an ios app - ios

Question

Let's say I want to use the rest api of some service, Twitbookr, to get a user's profile information. So I get the user to log in via my app and I get the credentials needed to make the call.
After this I load a new ViewController. I want to populate the fields in this view with the user's profile information. So I make my first call to the api:
[NSURLConnection sendAsynchronousRequest:req
queue:NSOperation.mainQueue
completionHandler:
^(NSURLResponse *response, NSData *data, NSError *error)
{
// successfully fetch data using credentials
// assume complete code here including dispatch_async etc
self.data = data;
})];
Then I want to use the data:
self.nameLabel.text = [self.data objectForKey:#"name"];
self.userid = [self.data objectForKey:#"userid"];
But the request hasn't finished yet, so the program throws an error.
And I want to make more calls to get different types of data, for example, the pictures from the frontpage album, which rely on the userid which I can only get from the request above. So how do I make my next subsequent call making sure I already have the userid from the first call?
What's the correct way to handle this situation?
Should I be using synchronous requests instead?
Should I put up a loading symbol until all of my requests are done? If so, how do I test that the requests have actually finished? And what's the point of them being asynchronous?

Answer 1

Try this
[NSURLConnection sendAsynchronousRequest:req
queue:NSOperation.mainQueue
completionHandler:
^(NSURLResponse *response, NSData *data, NSError *error)
{
// successfully fetch data using credentials
self.data = data;
//Use data here
dispatch_async(dispatch_get_main_queue(), ^{
//Update UI here
});
})];
When you use AsynchronousRequest,use data in completion block. I think your code
self.nameLabel.text = self.data.name;
is wrong,because self.data looks like NSData,and it not has a property of name
Update:As Mike said,only update UI on main thread.