NSMutableArray appears empty but is being populated - ios

Question

Am having a major problem with an NSMutableArray, I'm probably missing something really obvious - have probably been looking at it so much that I just can't see it.
Am reading some Tweets and then using the results to populate an NSMutableArray :
#synthesize testArray;
- (void)viewDidLoad{
[super viewDidLoad];
testArray = [[NSMutableArray alloc] init];
TWRequest *request = [[TWRequest alloc] initWithURL:[NSURL URLWithString:#"http://search.twitter.com/search.jsonq=kennedy&with_twitter_user_id=true&result_type=recent"]
parameters:nil requestMethod:TWRequestMethodGET];
[request performRequestWithHandler:^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error)
{
if ([urlResponse statusCode] == 200) {
// The response from Twitter is in JSON format
// Move the response into a dictionary
NSError *error;
NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:responseData options:0 error:&error];
NSArray *results = [dict objectForKey:#"results"];
//Loop through the results
for (NSDictionary *tweet in results) {
tweetStore *tweetDetails = [[tweetStore alloc] init];
NSString *twitText = [tweet objectForKey:#"text"];
//Save the tweet to the twitterText array
tweetDetails.name = #"test";
tweetDetails.date = #"test";
tweetDetails.tweet = twitText;
[testArray addObject:tweetDetails];
}
tweetStore *retrieveTweet = (tweetStore*)[testArray objectAtIndex:0];
NSLog(#"tweet is: %#", retrieveTweet.tweet);
//NSLog(#"Array is: %#", testArray); - *can* view Array etc here
}
else {
NSLog(#"Twitter error, HTTP response: %i", [urlResponse statusCode]);
}
}
];
NSLog(#"test array: %#", testArray); //Array is now empty......
}
I can view the array within the code where I've marked it, retrieve the objects I want etc, it works perfectly. But as soon as I try to access or display anything from the array outside of this then it seems to be empty. Any help or pointers would be appreciated.

Answer 1

The problem is that the code in the block is performed in an asynchronous way, so it is executed after the NSLog code.
The code executed follows this flow:
First you perform the initialization:
[super viewDidLoad];
testArray = [[NSMutableArray alloc] init];
TWRequest *request = [[TWRequest alloc] initWithURL:[NSURL URLWithString:#"http://search.twitter.com/search.jsonq=kennedy&with_twitter_user_id=true&result_type=recent"]
parameters:nil requestMethod:TWRequestMethodGET];
You start the request:
[request performRequestWithHandler:^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error) { <block_code> } ];
You print array information and it is empty (correct):
NSLog(#"test array: %#", testArray);
Now the asynchronous request ends and the code in the block is executed: so the array is populated correctly only in the block code.