How to split sections in UICollectionView? - ios

Question

I have a UICollectionView which implements pages organized into sections. I want to split a section into two parts and have the following logic. But UICollectionView doesn't seem to be happy with this:
func splitSection(at index: IndexPath) {
// this performs the logical split
self.document.splitSection(at: index)
if let cv = self.collectionView {
cv.performBatchUpdates({
let N = self.document.numberOfSection
let n = N - index.section - 1
let range = Range.init(uncheckedBounds: (index.section, n))
let affectedSections = IndexSet.init(integersIn: range)
cv.reloadSections(affectedSections)
let sections = IndexSet.init(integersIn: Range.init(uncheckedBounds: (N-1, 1)))
cv.insertSections(sections)
}, completion: { (_) in
// commit section updates
})
}
}

Answer 1

in numberOfSections function return 2
then in cellforitemat function use switch on indexpath.section

Answer 2

Ok. So I think I have solved the problem after various experimentation. Here is the final solution in case any one else gets into this problem.
The basic idea is:
Move all sections after the the section being split by 1
Insert a section after the section being split
Delete all the items after the split index from the current section
Insert all the items into the newly created section.
The reverse idea can be employed for merging the sections.
Here is the solution:
func splitSection(at index: IndexPath) {
# first get a list of deleted and inserted indices as a result of splitting
let (deleted, inserted) = self.document.splitSection(at: index)
if let cv = self.collectionView {
cv.performBatchUpdates({
let N = self.document.numberOfSection
// now move over the sections to make space for one more section.
for idx in index.section+1..<N-1 {
cv.moveSection(idx, toSection: idx+1)
}
// add a new section
cv.insertSections(IndexSet.init(integer: index.section+1))
// now perform item movements to finish splitting
cv.deleteItems(at: deleted)
cv.insertItems(at: inserted)
}, completion: { (_) in
self.document.updateSections()
})
}
}