Swift / CollectionViewWaterfallLayout / how to set cell amount - ios

Question

I'm using this CollectionViewWaterfallLayout.
The following functions sets the size of the cells randomly:
var testInteger = 10
lazy var cellSizes: [CGSize] = {
var _cellSizes = [CGSize]()
for _ in 0...10 {
let random = Int(arc4random_uniform((UInt32(100))))
_cellSizes.append(CGSize(width: 140, height: 50 + random))
}
return _cellSizes
}()
This: for _ in 0...10 sets the amount of the cells to 10, but since I'm downloading data from a web blog, I need to set it by var posts = [EventPosts]() -> posts.count, to be the amount of blog entrys that are downloaded. How can I do that?
I've tryed to use for _ in Int(posts.count), but it says, that Instant Member posts, can't be used on type ViewControllerXY.
Help is very appreciated.
Edit. This is the Custom Layout class.
//
// CollectionViewWaterfallLayout.swift
// CollectionViewWaterfallLayout
//
// Created by Eric Cerney on 7/21/14.
// Based on CHTCollectionViewWaterfallLayout by Nelson Tai
// Copyright (c) 2014 Eric Cerney. All rights reserved.
//
import UIKit
public let CollectionViewWaterfallElementKindSectionHeader = "CollectionViewWaterfallElementKindSectionHeader"
public let CollectionViewWaterfallElementKindSectionFooter = "CollectionViewWaterfallElementKindSectionFooter"
#objc public protocol CollectionViewWaterfallLayoutDelegate:UICollectionViewDelegate {
func collectionView(collectionView: UICollectionView, layout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize
optional func collectionView(collectionView: UICollectionView, layout: UICollectionViewLayout, heightForHeaderInSection section: Int) -> Float
optional func collectionView(collectionView: UICollectionView, layout: UICollectionViewLayout, heightForFooterInSection section: Int) -> Float
optional func collectionView(collectionView: UICollectionView, layout: UICollectionViewLayout, insetForSection section: Int) -> UIEdgeInsets
optional func collectionView(collectionView: UICollectionView, layout: UICollectionViewLayout, insetForHeaderInSection section: Int) -> UIEdgeInsets
optional func collectionView(collectionView: UICollectionView, layout: UICollectionViewLayout, insetForFooterInSection section: Int) -> UIEdgeInsets
optional func collectionView(collectionView: UICollectionView, layout: UICollectionViewLayout, minimumInteritemSpacingForSection section: Int) -> Float
}
public class CollectionViewWaterfallLayout: UICollectionViewLayout {
//MARK: Private constants
/// How many items to be union into a single rectangle
private let unionSize = 20;
//MARK: Public Properties
public var columnCount:Int = 2 {
didSet {
invalidateIfNotEqual(oldValue, newValue: columnCount)
}
}
public var minimumColumnSpacing:Float = 10.0 {
didSet {
invalidateIfNotEqual(oldValue, newValue: minimumColumnSpacing)
}
}
public var minimumInteritemSpacing:Float = 10.0 {
didSet {
invalidateIfNotEqual(oldValue, newValue: minimumInteritemSpacing)
}
}
public var headerHeight:Float = 0.0 {
didSet {
invalidateIfNotEqual(oldValue, newValue: headerHeight)
}
}
public var footerHeight:Float = 0.0 {
didSet {
invalidateIfNotEqual(oldValue, newValue: footerHeight)
}
}
public var headerInset:UIEdgeInsets = UIEdgeInsetsZero {
didSet {
invalidateIfNotEqual(NSValue(UIEdgeInsets: oldValue), newValue: NSValue(UIEdgeInsets: headerInset))
}
}
public var footerInset:UIEdgeInsets = UIEdgeInsetsZero {
didSet {
invalidateIfNotEqual(NSValue(UIEdgeInsets: oldValue), newValue: NSValue(UIEdgeInsets: footerInset))
}
}
public var sectionInset:UIEdgeInsets = UIEdgeInsetsZero {
didSet {
invalidateIfNotEqual(NSValue(UIEdgeInsets: oldValue), newValue: NSValue(UIEdgeInsets: sectionInset))
}
}
//MARK: Private Properties
private weak var delegate: CollectionViewWaterfallLayoutDelegate? {
get {
return collectionView?.delegate as? CollectionViewWaterfallLayoutDelegate
}
}
private var columnHeights = [Float]()
private var sectionItemAttributes = [[UICollectionViewLayoutAttributes]]()
private var allItemAttributes = [UICollectionViewLayoutAttributes]()
private var headersAttribute = [Int: UICollectionViewLayoutAttributes]()
private var footersAttribute = [Int: UICollectionViewLayoutAttributes]()
private var unionRects = [CGRect]()
//MARK: UICollectionViewLayout Methods
override public func prepareLayout() {
super.prepareLayout()
let numberOfSections = collectionView?.numberOfSections()
if numberOfSections == 0 {
return;
}
assert(delegate!.conformsToProtocol(CollectionViewWaterfallLayoutDelegate), "UICollectionView's delegate should conform to WaterfallLayoutDelegate protocol")
assert(columnCount > 0, "WaterfallFlowLayout's columnCount should be greater than 0")
// Initialize variables
headersAttribute.removeAll(keepCapacity: false)
footersAttribute.removeAll(keepCapacity: false)
unionRects.removeAll(keepCapacity: false)
columnHeights.removeAll(keepCapacity: false)
allItemAttributes.removeAll(keepCapacity: false)
sectionItemAttributes.removeAll(keepCapacity: false)
for _ in 0..<columnCount {
self.columnHeights.append(0)
}
// Create attributes
var top:Float = 0
var attributes: UICollectionViewLayoutAttributes
for section in 0..<numberOfSections! {
/*
* 1. Get section-specific metrics (minimumInteritemSpacing, sectionInset)
*/
var minimumInteritemSpacing: Float
if let height = delegate?.collectionView?(collectionView!, layout: self, minimumInteritemSpacingForSection: section) {
minimumInteritemSpacing = height
}
else {
minimumInteritemSpacing = self.minimumInteritemSpacing
}
var sectionInset: UIEdgeInsets
if let inset = delegate?.collectionView?(collectionView!, layout: self, insetForSection: section) {
sectionInset = inset
}
else {
sectionInset = self.sectionInset
}
let width = Float(collectionView!.frame.size.width - sectionInset.left - sectionInset.right)
let itemWidth = floorf((width - Float(columnCount - 1) * Float(minimumColumnSpacing)) / Float(columnCount))
/*
* 2. Section header
*/
var headerHeight: Float
if let height = delegate?.collectionView?(collectionView!, layout: self, heightForHeaderInSection: section) {
headerHeight = height
}
else {
headerHeight = self.headerHeight
}
var headerInset: UIEdgeInsets
if let inset = delegate?.collectionView?(collectionView!, layout: self, insetForHeaderInSection: section) {
headerInset = inset
}
else {
headerInset = self.headerInset
}
top += Float(headerInset.top)
if headerHeight > 0 {
attributes = UICollectionViewLayoutAttributes(forSupplementaryViewOfKind: CollectionViewWaterfallElementKindSectionHeader, withIndexPath: NSIndexPath(forItem: 0, inSection: section))
attributes.frame = CGRect(x: headerInset.left, y: CGFloat(top), width: collectionView!.frame.size.width - (headerInset.left + headerInset.right), height: CGFloat(headerHeight))
headersAttribute[section] = attributes
allItemAttributes.append(attributes)
top = Float(CGRectGetMaxY(attributes.frame)) + Float(headerInset.bottom)
}
top += Float(sectionInset.top)
for idx in 0..<columnCount {
columnHeights[idx] = top
}
/*
* 3. Section items
*/
let itemCount = collectionView!.numberOfItemsInSection(section)
var itemAttributes = [UICollectionViewLayoutAttributes]()
// Item will be put into shortest column.
for idx in 0..<itemCount {
let indexPath = NSIndexPath(forItem: idx, inSection: section)
let columnIndex = shortestColumnIndex()
let xOffset = Float(sectionInset.left) + Float(itemWidth + minimumColumnSpacing) * Float(columnIndex)
let yOffset = columnHeights[columnIndex]
let itemSize = delegate?.collectionView(collectionView!, layout: self, sizeForItemAtIndexPath: indexPath)
var itemHeight: Float = 0.0
if itemSize?.height > 0 && itemSize?.width > 0 {
itemHeight = Float(itemSize!.height) * itemWidth / Float(itemSize!.width)
}
attributes = UICollectionViewLayoutAttributes(forCellWithIndexPath: indexPath)
attributes.frame = CGRect(x: CGFloat(xOffset), y: CGFloat(yOffset), width: CGFloat(itemWidth), height: CGFloat(itemHeight))
itemAttributes.append(attributes)
allItemAttributes.append(attributes)
columnHeights[columnIndex] = Float(CGRectGetMaxY(attributes.frame)) + minimumInteritemSpacing
}
sectionItemAttributes.append(itemAttributes)
/*
* 4. Section footer
*/
var footerHeight: Float
let columnIndex = longestColumnIndex()
top = columnHeights[columnIndex] - minimumInteritemSpacing + Float(sectionInset.bottom)
if let height = delegate?.collectionView?(collectionView!, layout: self, heightForFooterInSection: section) {
footerHeight = height
}
else {
footerHeight = self.footerHeight
}
var footerInset: UIEdgeInsets
if let inset = delegate?.collectionView?(collectionView!, layout: self, insetForFooterInSection: section) {
footerInset = inset
}
else {
footerInset = self.footerInset
}
top += Float(footerInset.top)
if footerHeight > 0 {
attributes = UICollectionViewLayoutAttributes(forSupplementaryViewOfKind: CollectionViewWaterfallElementKindSectionFooter, withIndexPath: NSIndexPath(forItem: 0, inSection: section))
attributes.frame = CGRect(x: footerInset.left, y: CGFloat(top), width: collectionView!.frame.size.width - (footerInset.left + footerInset.right), height: CGFloat(footerHeight))
footersAttribute[section] = attributes
allItemAttributes.append(attributes)
top = Float(CGRectGetMaxY(attributes.frame)) + Float(footerInset.bottom)
}
for idx in 0..<columnCount {
columnHeights[idx] = top
}
}
// Build union rects
var idx = 0
let itemCounts = allItemAttributes.count
while idx < itemCounts {
let rect1 = allItemAttributes[idx].frame
idx = min(idx + unionSize, itemCounts) - 1
let rect2 = allItemAttributes[idx].frame
unionRects.append(CGRectUnion(rect1, rect2))
++idx
}
}
override public func collectionViewContentSize() -> CGSize {
let numberOfSections = collectionView?.numberOfSections()
if numberOfSections == 0 {
return CGSizeZero
}
var contentSize = collectionView?.bounds.size
contentSize?.height = CGFloat(columnHeights[0])
return contentSize!
}
override public func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes? {
if indexPath.section >= sectionItemAttributes.count {
return nil
}
if indexPath.item >= sectionItemAttributes[indexPath.section].count {
return nil
}
return sectionItemAttributes[indexPath.section][indexPath.item]
}
override public func layoutAttributesForSupplementaryViewOfKind(elementKind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes? {
var attribute: UICollectionViewLayoutAttributes?
if elementKind == CollectionViewWaterfallElementKindSectionHeader {
attribute = headersAttribute[indexPath.section]
}
else if elementKind == CollectionViewWaterfallElementKindSectionFooter {
attribute = footersAttribute[indexPath.section]
}
return attribute
}
override public func layoutAttributesForElementsInRect(rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
var begin:Int = 0
var end: Int = unionRects.count
var attrs = [UICollectionViewLayoutAttributes]()
for i in 0..<unionRects.count {
if CGRectIntersectsRect(rect, unionRects[i]) {
begin = i * unionSize
break
}
}
for i in (0..<unionRects.count).reverse() {
if CGRectIntersectsRect(rect, unionRects[i]) {
end = min((i+1) * unionSize, allItemAttributes.count)
break
}
}
for var i = begin; i < end; i++ {
let attr = allItemAttributes[i]
if CGRectIntersectsRect(rect, attr.frame) {
attrs.append(attr)
}
}
return Array(attrs)
}
override public func shouldInvalidateLayoutForBoundsChange(newBounds: CGRect) -> Bool {
let oldBounds = collectionView?.bounds
if CGRectGetWidth(newBounds) != CGRectGetWidth(oldBounds!) {
return true
}
return false
}
//MARK: Private Methods
private func shortestColumnIndex() -> Int {
var index: Int = 0
var shortestHeight = MAXFLOAT
for (idx, height) in columnHeights.enumerate() {
if height < shortestHeight {
shortestHeight = height
index = idx
}
}
return index
}
private func longestColumnIndex() -> Int {
var index: Int = 0
var longestHeight:Float = 0
for (idx, height) in columnHeights.enumerate() {
if height > longestHeight {
longestHeight = height
index = idx
}
}
return index
}
private func invalidateIfNotEqual(oldValue: AnyObject, newValue: AnyObject) {
if !oldValue.isEqual(newValue) {
invalidateLayout()
}
}
}

Answer 1

You should override this function:
override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes?
And then use this in prepareLayout():
// my collection only have one section,you can for-in all sections
for row in 0..<collectionView!.numberOfItemsInSection(0) {
allLayoutAttributes.append(layoutAttributesForItemAtIndexPath(NSIndexPath(forItem: row, inSection: 0))!)
}
And return all attributes at last :
override func layoutAttributesForElementsInRect(rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
return allLayoutAttributes
}