CollectionView Delegates called before URL Connection Finishes - ios

Question

I am implementing a CollectionView with URL Connection.
The problem that I have is as follows the collectionView delegates are called before the URL connection is finished. Therefore, Collection View does not get any data to display or how could I reload collection view.
Here is my implementation.
-(id)init{
self = [super init];
if (self){
[self loadFromURL];
}
return self;
}
-(void)loadFromURL{
NSURLRequest *theRequest = [NSURLRequest requestWithURL:
[NSURL URLWithString:#"http://www.appybyte.com/satgitsin/products.php?zip=77072"]];
NSURLConnection *theConnection=[[NSURLConnection alloc]
initWithRequest:theRequest delegate:self];
if(theConnection){
responseData = [[NSMutableData alloc] init];
} else {
NSLog(#"failed");
}
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
[responseData setLength:0];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[responseData appendData:data];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
NSString *msg = [NSString stringWithFormat:#"Failed: %#", [error description]];
NSLog(#"%#",msg);
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
NSError *myError = nil;
NSDictionary *res = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingMutableLeaves error:&myError];
self.pElements = [[NSMutableArray alloc] init];
for (NSDictionary *aModuleDict in res){
PMosaicData *aMosaicModule = [[PMosaicData alloc] initWithDictionary:aModuleDict];
[self.pElements addObject:aMosaicModule];
}
}
#pragma mark - UICollectionViewDataSource
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
return 1;
}
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
return [self.pElements count];
}
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
static NSString *cellIdentifier = #"cell";
PMosaicCell *pCell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];
PMosaicData *pData=[self.pElements objectAtIndex:indexPath.row];
pCell.pMosaicData = pData;
return pCell;
}
By the way, my collectionView is defined in another class called CustomViewController.h as __weak IBOutlet UICollectionView *_collectionView; How could I able to make it work?

Answer 1

at the end of your connectionDidFinishLoading: call [self.collectionView reloadData].
I would recommend using NSURLConnection's class method sendAsynchronousRequest:queue:options:error: instead of of the delegate pattern since you aren't doing any custom buffering logic.
The final code should look something like this:
-(void)loadFromURL {
NSURL *url = [NSURL URLWithString:#"http://www.appybyte.com/satgitsin/products.php?zip=77072"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
__weak typeof(self) weakSelf = self;
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
NSError *myError = nil;
NSDictionary *res = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:&myError];
// probably should handle the error here
if (myError) {
}
weakSelf.pElements = [[NSMutableArray alloc] init];
for (NSDictionary *aModuleDict in res){
PMosaicData *aMosaicModule = [[PMosaicData alloc] initWithDictionary:aModuleDict];
[weakSelf.pElements addObject:aMosaicModule];
}
[weakSelf.collectionView reloadData];
}];
}