Using UICollectionReusableView to group Cells - ios

Question

I'm having trouble updating my old code which made synchronous JSOn calls to a new one which makes asynchronous calls using AFNetworking.
In my old code I was grouping cells with a UICollectionReusableView using a date string ("release_date"), all of this was done in the viewDidLoad. Now with AFNetworking I moved everything out of the viewDidLoad, so I'm stuck trying to figure out how to merge my old code with my new one.
This is the new code I have to parse my JSON with AFNetworking:
- (void)viewDidLoad
{
[super viewDidLoad];
self.upcomingReleases = [[NSMutableArray alloc] init];
[self makeReleasesRequests];
[self.collectionView registerClass:[ReleaseCell class] forCellWithReuseIdentifier:#"ReleaseCell"];
}
-(void)makeReleasesRequests //AFNetworking Call
{
NSURL *url = [NSURL URLWithString:#"http://www.soleresource.com/upcoming.json"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
operation.responseSerializer = [AFJSONResponseSerializer serializer];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(#"#");
self.upcomingReleases = [responseObject objectForKey:#"upcoming_releases"];
[self.collectionView reloadData];
} failure:nil];
[operation start];
}
Code I had in my viewDidLoad before I started using AFNetworking to make JSON calls and "group" my cells:
- (void)viewDidLoad
{
[super viewDidLoad];
NSURL *upcomingReleaseURL = [NSURL URLWithString:#"http://www.soleresource.com/upcoming.json"];
NSData *jsonData = [NSData dataWithContentsOfURL:upcomingReleaseURL];
NSError *error = nil;
NSDictionary *dataDictionary = [NSJSONSerialization JSONObjectWithData:jsonData options:0 error:&error];
NSArray *upcomingReleasesArray = [dataDictionary objectForKey:#"upcoming_releases"];
//This is the dateFormatter we'll need to parse the release dates
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"];
NSTimeZone *est = [NSTimeZone timeZoneWithAbbreviation:#"EST"];
[dateFormatter setTimeZone:est];
[dateFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:#"en_US"]]; //A bit of an overkill to avoid bugs on different locales
//Temp array where we'll store the unsorted bucket dates
NSMutableArray *unsortedReleaseWeek = [[NSMutableArray alloc] init];
NSMutableDictionary *tmpDict = [[NSMutableDictionary alloc] init];
for (NSDictionary *upcomingReleaseDictionary in upcomingReleasesArray) {
//We find the release date from the string
NSDate *releaseDate = [dateFormatter dateFromString:[upcomingReleaseDictionary objectForKey:#"release_date"]];
//We create a new date that ignores everything that is not the actual day (ignoring stuff like the time of the day)
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components =
[gregorian components:(NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) fromDate:releaseDate];
//This will represent our releases "bucket"
NSDate *bucket = [gregorian dateFromComponents:components];
//We get the existing objects in the bucket and update it with the latest addition
NSMutableArray *releasesInBucket = [tmpDict objectForKey:bucket];
if (!releasesInBucket){
releasesInBucket = [NSMutableArray array];
[unsortedReleaseWeek addObject:bucket];
}
UpcomingRelease *upcomingRelease = [UpcomingRelease upcomingReleaseWithName:[upcomingReleaseDictionary objectForKey:#"release_name"]];
upcomingRelease.release_date = [upcomingReleaseDictionary objectForKey:#"release_date"];
upcomingRelease.release_date = [upcomingReleaseDictionary objectForKey:#"release_date"];
[releasesInBucket addObject:upcomingRelease];
[tmpDict setObject:releasesInBucket forKey:bucket];
}
[unsortedReleaseWeek sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
NSDate* date1 = obj1;
NSDate* date2 = obj2;
//This will sort the dates in ascending order (earlier dates first)
return [date1 compare:date2];
//Use [date2 compare:date1] if you want an descending order
}];
self.releaseWeekDictionary = [NSDictionary dictionaryWithDictionary:tmpDict];
self.releaseWeek = [NSArray arrayWithArray:unsortedReleaseWeek];
[self.collectionView registerClass:[ReleaseCell class] forCellWithReuseIdentifier:#"ReleaseCell"];
}
CollectionViewCell
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
static NSString *identifier = #"Cell";
ReleaseCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
// Part of my new code AFNetworking
NSDictionary *upcomingReleaseDictionary = [self.upcomingReleases objectAtIndex:indexPath.row];
//
// I had this in my old code
UpcomingRelease *upcomingRelease = [self.releaseWeekDictionary objectForKey:self.releaseWeek[indexPath.section]][indexPath.row];
//
cell.release_name.text = upcomingRelease.release_name;
return cell;
}
This is the rest:
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return [self.releaseWeek count];
}
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return [[self.releaseWeekDictionary objectForKey:self.releaseWeek[section]] count];
}
-(UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
ReleaseWeek *releaseWeek = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:#"releaseWeek" forIndexPath:indexPath];
//We tell the formatter to produce a date in the format "Name-of-the-month day"
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"MMMM dd"];
NSTimeZone *est = [NSTimeZone timeZoneWithAbbreviation:#"EST"];
[dateFormatter setTimeZone:est];
[dateFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:#"en_US"]];
//We read the bucket date and feed it to the date formatter
NSDate *releaseWeekDate = self.releaseWeek[indexPath.section];
releaseWeek.releaseDate.text = [[dateFormatter stringFromDate:releaseWeekDate] uppercaseString];
return releaseWeek;
}
I'm basically trying to figure out how to take the code that grouped my cells be the date string and integrate it with my new code.
Thanks.

Answer 1

Think MVC. Separate your model (the stuff that comes from the network) into a separate class that does the network operations, and grouping things into arrays and dictionaries. Your view controller should simply observe the model. You can use delegation or (my favorite) KVO to know when the model has updated data available. Then you just update your collection view. Your view controller should simply be an interface between the model and the views. If you separate things out this way you will find that it is much more natural, and you aren't fighting against the system.

Answer 2

You are closer than you think.
Simply put everything you used to do in viewDidLoad: (everything between the assignment of jsonData to the registration of your collection view class) into the callback block of your AFNetworking call (where jsonData is now called responseObject).
At the end of the callback block, simply invoke [self.collectionView reloadData], and the your collection view will reload itself (i.e. call numberOfItems and cellForItemAtIndexPath for each item).
In your UICollectionViewDataSource methods that return the number of sections and items, simply return 0 if the properties that hold your model are nil or empty.
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
// Correctly returns 0 if nil or empty.
return [self.releaseWeek count];
}
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
if(!self.releaseWeekDictionary[section] || !self.releaseWeek[section]) {
return 0;
}else{
return [self.releaseWeekDictionary[self.releaseWeek[section]] count];
}
}
Below should be the gravy code in your completion block.
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(#"#");
NSArray *upcomingReleasesArray = [dataDictionary objectForKey:#"upcoming_releases"];
//This is the dateFormatter we'll need to parse the release dates
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"];
NSTimeZone *est = [NSTimeZone timeZoneWithAbbreviation:#"EST"];
[dateFormatter setTimeZone:est];
[dateFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:#"en_US"]]; //A bit of an overkill to avoid bugs on different locales
//Temp array where we'll store the unsorted bucket dates
NSMutableArray *unsortedReleaseWeek = [[NSMutableArray alloc] init];
NSMutableDictionary *tmpDict = [[NSMutableDictionary alloc] init];
for (NSDictionary *upcomingReleaseDictionary in upcomingReleasesArray) {
//We find the release date from the string
NSDate *releaseDate = [dateFormatter dateFromString:[upcomingReleaseDictionary objectForKey:#"release_date"]];
//We create a new date that ignores everything that is not the actual day (ignoring stuff like the time of the day)
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components =
[gregorian components:(NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) fromDate:releaseDate];
//This will represent our releases "bucket"
NSDate *bucket = [gregorian dateFromComponents:components];
//We get the existing objects in the bucket and update it with the latest addition
NSMutableArray *releasesInBucket = [tmpDict objectForKey:bucket];
if (!releasesInBucket){
releasesInBucket = [NSMutableArray array];
[unsortedReleaseWeek addObject:bucket];
}
UpcomingRelease *upcomingRelease = [UpcomingRelease upcomingReleaseWithName:[upcomingReleaseDictionary objectForKey:#"release_name"]];
upcomingRelease.release_date = [upcomingReleaseDictionary objectForKey:#"release_date"];
upcomingRelease.release_date = [upcomingReleaseDictionary objectForKey:#"release_date"];
[releasesInBucket addObject:upcomingRelease];
[tmpDict setObject:releasesInBucket forKey:bucket];
}
[unsortedReleaseWeek sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
NSDate* date1 = obj1;
NSDate* date2 = obj2;
//This will sort the dates in ascending order (earlier dates first)
return [date1 compare:date2];
//Use [date2 compare:date1] if you want an descending order
}];
self.releaseWeekDictionary = [NSDictionary dictionaryWithDictionary:tmpDict];
self.releaseWeek = [NSArray arrayWithArray:unsortedReleaseWeek];
[self.collectionView reloadData];
} failure:nil];
Edit: In your code, you were no longer assigning anything to upcomingReleases (block of commented code lines 91-102), and you were crashing referencing the index that didn't exist in the array. The fix is easy:
109: self.upcomingReleases = [dataDictionary objectForKey:#"upcoming_releases"];
122: for (NSDictionary *upcomingReleaseDictionary in self.upcomingReleases) {