Fill UICollectionViewCells in UICollectionView with data from an array programmatically - ios

Question

I have a UICollectionView which I would like to populate it with 100 UICollectionViewCells each with its own unique UILabel with text fetched from an array. I'd like to do this programmatically (without the Storyboard).
I've attempted it as posted below, but for some reason only the first cell renders properly.
// Setting up the UICollectionView
- (void)setupCollectionView {
UICollectionViewFlowLayout *layout=[[UICollectionViewFlowLayout alloc] init];
CGRect newFrame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height * 0.5);
self.collectionView=[[UICollectionView alloc] initWithFrame:newFrame collectionViewLayout:layout];
[self.collectionView setDataSource:self];
[self.collectionView setDelegate:self];
[self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:#"cellIdentifier"];
[self.collectionView setBackgroundColor:[UIColor clearColor]];
[self.view addSubview:self.collectionView];
}
//Trying to generate the unique cells with data
- (UICollectionViewCell *) collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
cell.backgroundColor = [UIColor yellowColor];
UILabel *label = [[UILabel alloc] initWithFrame: cell.frame];
label.text = [self.array objectAtIndex: indexPath.row];
label.textColor = [UIColor blackColor];
[cell.contentView addSubview:label];
return cell;
}
To note: my array is of size 100 with randomly generated numbers.
Your help is appreciated :)
Thanks!

Answer 1

The array's frame should be related to the bounds of its cell, not its cell's frame, who's origin will grow as the indexPath grows. Also, we don't want to unconditionally create the labels, since the cells get reused. Only create a label if one doesn't exist....
UILabel *label = (UILabel *)[cell viewWithTag:99];
if (!label) {
label = [[UILabel alloc] initWithFrame: cell.bounds]; // note use bounds here - which we want to be zero based since we're in the coordinate system of the cell
label.tag = 99;
label.text = [self.array objectAtIndex: indexPath.row];
label.textColor = [UIColor blackColor];
[cell.contentView addSubview:label];
}
// unconditionally setup its text
NSNumber *number = self.myArrayOfRandomNumbers[indexPath.row];
label.text = [number description];