UIViewController does not load its UICollectionView property - ios

Question

I have a UITabBarController that contains 2 UIViewControllers. The 2nd UIViewController crashes when ever I try to show from the 1st UIViewController.
The 2nd UIViewController crashes because of its UICollectionView declared as a private property.
I get a EXC_BAD_ACCESS so I think that the 2nd UIViewController tries to do [self setCollectionView] but when its property self.collectionView is not init yet (still nil).
I don't understand why it behaves so - I have no problem implementing the UICollectionView the same way in the 1st UIViewController. Here is the .m file of the 2nd UIViewController :
#interface WorkoutViewController () <UICollectionViewDataSource, UICollectionViewDelegate, DAPageControlViewDelegate>
#property (strong, nonatomic) UICollectionView *collectionView;
#property (strong, nonatomic) DAPageControlView *pageControlView;
#end
#implementation WorkoutViewController
- (void)viewDidLoad {
[super viewDidLoad];
[self createCollectionView];
[self createPageView];
// Constraints
// CollectionView
[self.collectionView mas_makeConstraints:^(MASConstraintMaker *make) {
make.edges.equalTo(self.view);
}];
// PageControl
[self.pageControlView mas_makeConstraints:^(MASConstraintMaker *make) {
make.trailing.equalTo(self.view);
make.leading.equalTo(self.view);
make.height.equalTo(screenAdjustedSizeFrom(15));
make.bottom.equalTo(self.view).offset(screenAdjustedSizeFrom(-15).floatValue);
}];
// Wake up collectionView
[self.collectionView reloadData];
}
-(void)createCollectionView {
// Layout
UICollectionViewFlowLayout *collectionViewLayout = [[UICollectionViewFlowLayout alloc] init];
collectionViewLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
// UICollectionView
self.collectionView = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:collectionViewLayout];
self.collectionView.dataSource = self;
self.collectionView.delegate = self;
[self.view addSubview:self.collectionView];
// Behavior
self.collectionView.pagingEnabled = YES;
// Appearance
self.collectionView.backgroundColor = [Color colorWithName:nil alpha:0.2f];
self.collectionView.showsHorizontalScrollIndicator = NO;
// Register cells
//[self.collectionView registerClass:[TrackingSetCollectionViewCell class] forCellWithReuseIdentifier:TrackingSetCollectionViewCellIdentifier]; }
-(void)createPageView {
// Support for pagination - DAPageControlView
self.pageControlView = [[DAPageControlView alloc] initWithFrame:CGRectZero];
self.pageControlView.delegate = self;
[self.view addSubview:self.pageControlView];
self.pageControlView.hidden = YES; // do not show the dots
}
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
return 1;
}
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return fetchManagedObjectsFromEntity(#"Autor", #[[NSSortDescriptor sortDescriptorWithKey:#"autorID" ascending:YES]], nil, self.managedObjectContext).count + 1; // +1 for testing !
}
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
//test
UICollectionViewCell *cell = [self.collectionView dequeueReusableCellWithReuseIdentifier:#"cell" forIndexPath:indexPath];
if (indexPath.row==0) {
cell.backgroundColor = [UIColor blueColor];
}
if (indexPath.row==1) {
cell.backgroundColor = [UIColor redColor];
}
return cell;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
return self.collectionView.bounds.size;
}
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section {
return 0.0;
}
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
return UIEdgeInsetsMake(0, 0, 0, 0);
}
#pragma mark - DAPageControlView Delegate
- (void)pageControlViewDidChangeCurrentPage:(DAPageControlView *)pageControlView
{
[self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForRow:pageControlView.currentPage inSection:0] atScrollPosition:UICollectionViewScrollPositionNone animated:NO];
}

Answer 1

Problem solved - I forgot to register a class for the UICollectionViewCell. I thought it was not necessary for to do so for the 'default' class UICollectionViewCell but since the UICollectionView is added programmatically, it makes sense.