My UICollectionViewLayout subclass

gistfile1.m

//
//  BJUPortraitLayout.m
//  BizjournalsUniversal
//
//  Created by Wess Cope on 1/7/13.
//  Copyright (c) 2013 ACBJ. All rights reserved.
//

#import "BJUPortraitLayout.h"
#import "Archimedes.h"

static CGFloat const kBJUCollectionLayoutTopHeight  = 300.0f;

@interface BJUPortraitLayout()
@property (strong, nonatomic) NSMutableArray *pendingAttributes;
@end

@implementation BJUPortraitLayout

- (id)init
{
    self = [super init];
    if (self)
    {
        self.collectionView.pagingEnabled = YES;
        self.pendingAttributes  = [NSMutableArray new];
    }
    return self;
}

//- (void)prepareLayout
//{
//    
//}

- (CGSize)collectionViewContentSize
{
    CGFloat width = self.collectionView.numberOfSections * self.collectionView.width;
    CGFloat height = self.collectionView.height;
    
    return CGSizeMake(width, height);
}

- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
{
    return YES;
}

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSIndexPath *headlinePath           = [NSIndexPath indexPathForRow:0 inSection:0];
    NSIndexPath *adPath                 = [NSIndexPath indexPathForRow:1 inSection:0];
    NSIndexPath *subArticleOnePath      = [NSIndexPath indexPathForRow:2 inSection:0];
    NSIndexPath *subArticleTwoPath      = [NSIndexPath indexPathForRow:3 inSection:0];
    NSIndexPath *subArticleThreePath    = [NSIndexPath indexPathForRow:4 inSection:0];
    NSIndexPath *subArticleFourPath     = [NSIndexPath indexPathForRow:5 inSection:0];
    
    UICollectionViewLayoutAttributes *headlineAttributes        = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:headlinePath];
    UICollectionViewLayoutAttributes *adAttributes              = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:adPath];
    UICollectionViewLayoutAttributes *subArticleOneAttributes   = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:subArticleOnePath];
    UICollectionViewLayoutAttributes *subArticleTwoAttributes   = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:subArticleTwoPath];
    UICollectionViewLayoutAttributes *subArticleThreeAttributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:subArticleThreePath];
    UICollectionViewLayoutAttributes *subArticleFourAttributes  = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:subArticleFourPath];
    
    CGRect visibleRect = rect;

    CGFloat subArticleWidth  = (visibleRect.size.width / 2);
    CGFloat subArticleHeight = ((visibleRect.size.height - kBJUCollectionLayoutTopHeight) / 2);
    
    CGRect headlineFrame        = CGRectMake(visibleRect.origin.x, 0.0f, visibleRect.size.width - kBJUCollectionLayoutTopHeight, kBJUCollectionLayoutTopHeight);
    CGRect adFrame              = CGRectMake(headlineFrame.size.width, 0.0f, kBJUCollectionLayoutTopHeight, kBJUCollectionLayoutTopHeight);
    CGRect subArticleOneFrame   = CGRectMake(visibleRect.origin.x, kBJUCollectionLayoutTopHeight, subArticleWidth, subArticleHeight);
    CGRect subArticleTwoFrame   = CGRectMake(subArticleWidth, kBJUCollectionLayoutTopHeight, subArticleWidth, subArticleHeight);
    CGRect subArticleThreeFrame = CGRectMake(visibleRect.origin.x, kBJUCollectionLayoutTopHeight + subArticleHeight, subArticleWidth, subArticleHeight);
    CGRect subArticleFourFrame  = CGRectMake(subArticleWidth, kBJUCollectionLayoutTopHeight + subArticleHeight, subArticleWidth, subArticleHeight);
    
    headlineAttributes.frame        = headlineFrame;
    adAttributes.frame              = adFrame;
    subArticleOneAttributes.frame   = subArticleOneFrame;
    subArticleTwoAttributes.frame   = subArticleTwoFrame;
    subArticleThreeAttributes.frame = subArticleThreeFrame;
    subArticleFourAttributes.frame  = subArticleFourFrame;

    headlineAttributes.center           = CGRectCenterPoint(headlineFrame);
    adAttributes.center                 = CGRectCenterPoint(adFrame);
    subArticleOneAttributes.center      = CGRectCenterPoint(subArticleOneFrame);
    subArticleTwoAttributes.center      = CGRectCenterPoint(subArticleTwoFrame);
    subArticleThreeAttributes.center    = CGRectCenterPoint(subArticleThreeFrame);
    subArticleFourAttributes.center     = CGRectCenterPoint(subArticleFourFrame);
    
    headlineAttributes.size           = headlineFrame.size;
    adAttributes.size                 = adFrame.size;
    subArticleOneAttributes.size      = subArticleOneFrame.size;
    subArticleTwoAttributes.size      = subArticleTwoFrame.size;
    subArticleThreeAttributes.size    = subArticleThreeFrame.size;
    subArticleFourAttributes.size     = subArticleFourFrame.size;
    
    
    self.pendingAttributes = [@[headlineAttributes, adAttributes, subArticleOneAttributes, subArticleTwoAttributes, subArticleThreeAttributes, subArticleFourAttributes] mutableCopy];
    
    return self.pendingAttributes;
}

- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
    NSUInteger index = [indexPath indexAtPosition:1];
    UICollectionViewLayoutAttributes *layoutAttributes = self.pendingAttributes[index];
    
    return layoutAttributes;
}


//- (UICollectionViewLayoutAttributes *)initialLayoutAttributesForAppearingItemAtIndexPath:(NSIndexPath *)itemIndexPath
//{
//    NSUInteger index = [itemIndexPath indexAtPosition:1];
//    UICollectionViewLayoutAttributes *layoutAttributes = self.pendingAttributes[index];
//    
//    return layoutAttributes;
//}
//
//- (UICollectionViewLayoutAttributes *)finalLayoutAttributesForDisappearingItemAtIndexPath:(NSIndexPath *)itemIndexPath
//{
//    NSUInteger index = [itemIndexPath indexAtPosition:1];
//    UICollectionViewLayoutAttributes *layoutAttributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:itemIndexPath];
//    UICollectionViewLayoutAttributes *layoutAttributesOrigin = self.pendingAttributes[index];
//    
//    layoutAttributes.size   = layoutAttributesOrigin.size;
//    layoutAttributes.center = layoutAttributesOrigin.center;
//    
//    return layoutAttributes;   
//}

@end