Pass the Parsed Data to UICollectionView - ios

Question

I'm a junior level developer and I'm stuck at this very simple thing which I'm unable to figure out.
I've a class which is AFHTTPRequestOperationManager extended. Means it's #interface apiClient : AFHTTPRequestOperationManager in this class I've all my code which fetch images from Imgur API and using AFNetworking I've parsed the data upto a level where I start getting only the link of the images.Now the rootViewController which is a UICollectionViewController extended. In it's viewDidLoad I send a call to my APIClient and it start moving from methods to methods and finally give me an NSMutableArray which contains the images link I'll use in the UIImageView of my CollectionViewCell.
The Question is I'm using this to send the final links back to my rootViewController i.e. GalleryCollectionViewController
GalleryCollectionViewController *gcvc = [[GalleryCollectionViewController alloc] init];
[gcvc recieveGalleryImagesLinks:galleryImgLinkArr];
The problem is that in gcvc it calls numberOfItemsInSection before it can get any response from the API. So that means the count goes out zero and hence it is not displaying the data. So how can I get it to get the API call from apiClient class first and then make the viewController. I hope I've clearly stated my problem and if there is a need of sharing any more code I'll do it.
UPDATE
After authorization this methods gets the gallery images:
- (void)galleryAlbum:(NSString *)ID {
NSLog(#"ID is %#", ID);
[self GET:[NSString stringWithFormat:#"%#3/gallery/album/%#", self.baseURL,ID] parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {
self.galleryData = (NSDictionary *)responseObject;
galleryDataArr = [[NSMutableArray alloc] init];
galleryDataArr = [self.galleryData valueForKey:#"data"];
galleryImagesArr = [[NSMutableArray alloc] init];
galleryImagesArr = [galleryDataArr valueForKey:#"images"];
galleryImgLinkArr = [[NSMutableArray alloc] init];
galleryImgLinkArr = [galleryImagesArr valueForKey:#"link"];
GalleryCollectionViewController *gcvc = [[GalleryCollectionViewController alloc] init];
[gcvc recieveGalleryImagesLinks:galleryImgLinkArr];
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"Failed #2");
}];
}
Here gcvc is receiving the array with images link and then reloading the collection view as:
-(void)recieveGalleryImagesLinks:(NSMutableArray *)array
{
self.imageLinks = [[NSMutableArray alloc] initWithArray:array];
NSLog(#"Array: %#",self.imageLinks);
[self.collectionView reloadData];
}
But it's giving "UICollectionView: must be initialized with a non-nil layout parameter" although the array is not empty.

Answer 1

This line of code below is incorrect:
GalleryCollectionViewController *gcvc = [[GalleryCollectionViewController alloc] init];
[gcvc recieveGalleryImagesLinks:galleryImgLinkArr];
You need to use a blocks or delegate approach here which will pass back the array back to your collectionViewController and reload the collecrionView.
Even your method call from API class seems to be correct for delegate approach but make it a protocal method. This way you need not have to change much. It will be something like below:
[self.delegate recieveGalleryImagesLinks:galleryImgLinkArr
And when are calling API and is waiting for response show activityIndicator for loading data.