https://stackoverflow.com/questions/39691358/problems-reordering-collection-view-cell-with-custom-dimensions

CustomCellSizeViewController.swift

import UIKit

class ViewController: UIViewController {
	
	let sourceText : String = "So Midas, king of Lydia, swelled at first with pride when he found he could transform everything he touched to gold; but when he beheld his food grow rigid and his drink harden into golden ice then he understood that this gift was a bane and in his loathing for gold, cursed his prayer"
	
	var sourceData : [String]! {
		didSet {
			let dimensions : [CGSize] = {
				var d : [CGSize] = [CGSize]()
				let font = UIFont.systemFont(ofSize: 17)
				let fontAttributes = [NSFontAttributeName : font]
				print(sourceData)
				for item in sourceData {
					let stringSize = ((item + " ") as NSString).size(attributes: fontAttributes)
					d.append(CGSize(width: stringSize.width, height: stringSize.height))
				}
				return d
			}()
			
			if self.sortedLayout != nil {
				sortedLayout.dimensions = dimensions
				if let _ = sortedCVController {
					(sortedCVController as! bespokeCollectionViewController).sourceData = sourceData
				}
				self.sortedLayout.cache.removeAll()
				self.sortedLayout.prepare()
				if let _ = self.sortedCVController {
					
					self.sortedCVController.collectionView?.reloadData()
				}
			}
		}
	}
	var sortedCVController : UICollectionViewController!
	var sortedLayout : bespokeCollectionViewLayout!
	var sortButton : UIButton!
	var sortDirection : Int = 0
	
	override func viewDidLoad() {
		super.viewDidLoad()
		// Do any additional setup after loading the view, typically from a nib.
		
		sortedLayout = bespokeCollectionViewLayout(contentWidth: view.frame.width - 200)
		sourceData = {
			let components = sourceText.components(separatedBy: " ")
			return components
		}()
		
		sortedCVController = bespokeCollectionViewController(sourceData: sourceData, collectionViewLayout: sortedLayout, frame: CGRect(origin: CGPoint(x: 100, y: 100), size: CGSize(width: view.frame.width - 200, height: view.frame.height - 200)))
		sortedCVController.collectionView!.frame = CGRect(origin: CGPoint(x: 100, y: 100), size: CGSize(width: view.frame.width - 200, height: view.frame.height - 200))
		
		sortButton = {
			let sB : UIButton = UIButton(frame: CGRect(origin: CGPoint(x: 25, y: 100), size: CGSize(width: 50, height: 50)))
			sB.setTitle("Sort", for: .normal)
			sB.setTitleColor(UIColor.black, for: .normal)
			sB.addTarget(self, action: #selector(sort), for: .touchUpInside)
			sB.layer.borderColor = UIColor.black.cgColor
			sB.layer.borderWidth = 1.0
			return sB
		}()
		
		view.addSubview(sortedCVController.collectionView!)
		view.addSubview(sortButton)
	}
	
	
	func sort() -> Void {
		sourceData = sortDirection > 0 ? sourceData.sorted(by: { $0 > $1 }) : sourceData.sorted(by: { $0 < $1 })
		sortDirection = sortDirection + 1 > 1 ? 0 : 1
	}
	
}

class bespokeCollectionViewController : UICollectionViewController {
	
	var sourceData : [String]
	
	init(sourceData: [String], collectionViewLayout: bespokeCollectionViewLayout, frame: CGRect) {
		self.sourceData = sourceData
		super.init(collectionViewLayout: collectionViewLayout)
		
		self.collectionView = UICollectionView(frame: frame, collectionViewLayout: collectionViewLayout)
		self.collectionView?.backgroundColor = UIColor.white
		self.collectionView?.layer.borderColor = UIColor.black.cgColor
		self.collectionView?.layer.borderWidth = 1.0
		
		self.installsStandardGestureForInteractiveMovement = false
		
		let pangesture = UIPanGestureRecognizer(target: self, action: #selector(handlePanGesture(gesture:)))
		self.collectionView?.addGestureRecognizer(pangesture)
	}
	
	required init?(coder aDecoder: NSCoder) {
		fatalError("init(coder:) has not been implemented")
	}
	
	func handlePanGesture(gesture: UIPanGestureRecognizer) {
		switch gesture.state {
		case UIGestureRecognizerState.began:
			guard let selectedIndexPath = self.collectionView?.indexPathForItem(at: gesture.location(in: self.collectionView)) else { break }
			
			collectionView?.beginInteractiveMovementForItem(at: selectedIndexPath)
			print("Interactive movement began")
		case UIGestureRecognizerState.changed:
			collectionView?.updateInteractiveMovementTargetPosition(gesture.location(in: gesture.view))
			print("Interactive movement changed")
		case UIGestureRecognizerState.ended:
			collectionView?.endInteractiveMovement()
			print("Interactive movement ended")
		default:
			collectionView?.cancelInteractiveMovement()
			print("Interactive movement canceled")
		}
	}
	
	override func numberOfSections(in collectionView: UICollectionView) -> Int {
		guard !(self.collectionViewLayout as! bespokeCollectionViewLayout).cache.isEmpty else { return 0 }
		
		return (self.collectionViewLayout as! bespokeCollectionViewLayout).cache.last!.indexPath.section + 1
	}
	
	override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
		guard !(self.collectionViewLayout as! bespokeCollectionViewLayout).cache.isEmpty else { return 0 }
		
		var n : Int = 0
		for element in (self.collectionViewLayout as! bespokeCollectionViewLayout).cache {
			if element.indexPath.section == section {
				if element.indexPath.row > n {
					n = element.indexPath.row
				}
			}
		}
		print("Section \(section) has \(n) elements")
		return n + 1
	}
	
	override func collectionView(_ collectionView: UICollectionView, moveItemAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {
		let change = sourceData[sourceIndexPath.row]
		
		sourceData.remove(at: sourceIndexPath.row)
		sourceData.insert(change, at: destinationIndexPath.row)
	}
	
	override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
		collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "cell")
		
		let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)
		
		// Clean
		for subview in cell.subviews {
			subview.removeFromSuperview()
		}
		
		let label : UILabel = {
			let l : UILabel = UILabel()
			l.font = UIFont.systemFont(ofSize: 17)
			l.frame = CGRect(origin: CGPoint.zero, size: cell.frame.size)
			l.textColor = UIColor.black
			
			let index : Int = {
				var i : Int = 0
				for sectionCount in 0..<indexPath.section {
					i += (self.collectionView?.numberOfItems(inSection: sectionCount))!
				}
				i += indexPath.row
				return i
			}()
			
			l.text = sourceData[index]
			return l
		}()
		
		cell.addSubview(label)
		
		return cell
	}
	
}


class bespokeCollectionViewLayout : UICollectionViewLayout {
	
	var cache : [UICollectionViewLayoutAttributes] = [UICollectionViewLayoutAttributes]()
	let contentWidth: CGFloat
	var dimensions : [CGSize]!
	
	init(contentWidth: CGFloat) {
		self.contentWidth = contentWidth
		
		super.init()
	}
	
	required init?(coder aDecoder: NSCoder) {
		fatalError("init(coder:) has not been implemented")
	}
	
	override func prepare() -> Void {
		guard self.dimensions != nil else { return }
		if cache.isEmpty {
			var xOffset : CGFloat = 0
			var yOffset : CGFloat = 0
			
			var rowCount = 0
			var wordCount : Int = 0
			
			while wordCount < dimensions.count {
				let nextRowCount : Int = {
					var totalWidth : CGFloat = 0
					var numberOfWordsInRow : Int = 0
					
					while totalWidth < contentWidth && wordCount < dimensions.count {
						if totalWidth + dimensions[wordCount].width >= contentWidth {
							break
						}
						else
						{
							totalWidth += dimensions[wordCount].width
							wordCount += 1
							numberOfWordsInRow += 1
						}
						
					}
					return numberOfWordsInRow
				}()
				
				var columnCount : Int = 0
				for count in (wordCount - nextRowCount)..<wordCount {
					let index : IndexPath = IndexPath(row: columnCount, section: rowCount)
					let newAttribute : UICollectionViewLayoutAttributes = UICollectionViewLayoutAttributes(forCellWith: index)
					let cellFrame : CGRect = CGRect(origin: CGPoint(x: xOffset, y: yOffset), size: dimensions[count])
					newAttribute.frame = cellFrame
					cache.append(newAttribute)
					
					xOffset += dimensions[count].width
					columnCount += 1
				}
				
				xOffset = 0
				yOffset += dimensions[0].height
				
				rowCount += 1
				
			}
		}
		print(cache)
	}
	
	override var collectionViewContentSize: CGSize {
		guard !cache.isEmpty else { return CGSize(width: 100, height: 100) }
		return CGSize(width: self.contentWidth, height: cache.last!.frame.maxY)
	}
	
	override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
		var layoutAttributes = [UICollectionViewLayoutAttributes]()
		if cache.isEmpty {
			self.prepare()
		}
		for attributes in cache {
			if attributes.frame.intersects(rect) {
				layoutAttributes.append(attributes)
			}
		}
		return layoutAttributes
	}
}