UICollectionView datasource understanding issue - ios

Question

I have confused with datasource of UIColectionView and I really need help here.
I have array with objects [#"1", #"2", #"3", #"4", #"5", #"6"]
So I need to display them
1 2 3
4 5 6
I have found this code
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return noOfItem/ noOfSection;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return noOfSection;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"cellRecipe";
collectionCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
;
Employee *emp = [array_ objectAtIndex:indexPath.section * noOfSection + indexPath.row];
cell.name.text = emp.name;
cell.image.image = emp.thumbImg;
return cell;
}
but I think it is not good use noOfItem/ noOfSection
so for example if I have 20 objects and 3 items per section
I got this error
-[__NSArrayM objectAtIndex:]: index 20 beyond bounds [0 .. 19]'
because each my section has 3 items

Answer 1

In my opinion you aren't quite approaching UICollectionView in the correct way.
Sections are meant to be separate sections of content, not the number of rows.
Items in section is meant to return the number of items for a given section.
In your example I would do it like this:
/**
* Called after the controller’s view is loaded into memory.
*/
- (void)viewDidLoad
{
[super viewDidLoad];
self.employees = #[[[Employee alloc] init], [[Employee alloc] init], [[Employee alloc] init], [[Employee alloc] init], [[Employee alloc] init]];
}
/**
* Asks the data source for the number of sections in the collection view.
*
* #param collectionView An object representing the collection view requesting this information.
*
* #return The number of sections in collectionView.
*/
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}
/**
* Asks the data source for the cell that corresponds to the specified item in the collection view.
*
* #param collectionView An object representing the collection view requesting this information.
* #param indexPath The index path that specifies the location of the item.
*
* #return A configured cell object. You must not return nil from this method.
*/
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"cellRecipe";
collectionCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
Employee *employee = self.items[indexPath.item];
cell.name.text = employee.name;
cell.image.image = employee.thumbImg;
return cell;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return self.items.count;
}

Answer 2

With reference to an array containing [#"1", #"2", #"3", #"4", #"5", #"6"]
You don't need this method :
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
Now do this :
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return [self.arrayName count];
}
Now you need to set the size of cell so that each row can have 3 items. You can either set the size of cell using storyboard or you can use this method:
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath

Answer 3

True. You don't really need numberOfSections... as you can solve this with sizing of cells (autolayout is your friend). If using the numberOfSectionsInCollectionView, you need to catch that the last section only has two items. You didn't include how you calculate noOfSection.
In the numberOfItems... method, you can do this:
if (section == noOfSection) {
return noOfItem % noOfSection; // Finding the remainder with modulo
} else {
return noOfItem / noOfSection;
}
I haven't tested this, but believe it should work.