UICollectionViewFlowLayout class that positions the CollectionView Header and Footer views horizontally to the section items. This was used to create a Calendar Week view with one cell per section (representing the day of the week) and the Section header to the left of it and a footer to the right. The other sections were the other days of the w…

CollectionViewCalendarFlowLayout.m

//
//  CollectionViewCalendarFlowLayout.m


#import "CollectionViewCalendarFlowLayout.h"

#define HEADER_WIDTH 200.0f
#define FOOTER_WIDTH 20.0f
#define SECTION_MARGIN_X 0.0f
#define PADDING_X 0.0f
#define WEEKEND_CELL_HEIGHT 100.0f

@interface CollectionViewCalendarFlowLayout (){
    
    UIInterfaceOrientation _orientation;
}

-(void)initLayoutProperties;

@end

@implementation CollectionViewCalendarFlowLayout

-(void)prepareLayout {
        
    [super prepareLayout];
    [self initLayoutProperties];
}

-(void)initLayoutProperties {
    
    _orientation = [[UIApplication sharedApplication] statusBarOrientation];
    
    CGRect viewFrame = self.collectionView.frame;
    CGFloat cellHeight = (viewFrame.size.height/7)-2;
    
    self.itemSize = CGSizeMake(cellHeight, cellHeight); // width will change based on visible view
    
    /*
        If you make the default header/footer size 0.0 it doesn't attempt to add the views.
        If you don't offset the default size we get a gap between items.
     */
    self.headerReferenceSize = CGSizeMake(1.0f, 1.0f);
    self.footerReferenceSize = CGSizeMake(1.0f, 1.0f);
    //self.sectionInset = UIEdgeInsetsMake(-1.0f, 0.0f, -1.0f, 0.0f);
    self.sectionInset = UIEdgeInsetsMake(0.0f, 0.0f, 0.0f, 0.0f);
    self.minimumLineSpacing = 0.0f;
    self.minimumInteritemSpacing = 0.0f;
}

/*
    Return attributes for items
 */

-(NSArray*)layoutAttributesForElementsInRect:(CGRect)rect {
    
    NSArray* array = [super layoutAttributesForElementsInRect:rect];
    
    for(UICollectionViewLayoutAttributes* attributes in array) {
        
        UICollectionViewLayoutAttributes *suppViewAttributes;
        
        if([[attributes representedElementKind] isEqualToString:UICollectionElementKindSectionHeader]){
            
            suppViewAttributes = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionHeader atIndexPath:[attributes indexPath]];
            [attributes setFrame:[suppViewAttributes frame]];
            
        }else if([[attributes representedElementKind] isEqualToString:UICollectionElementKindSectionFooter]){
            
            suppViewAttributes = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionFooter atIndexPath:[attributes indexPath]];
            [attributes setFrame:[suppViewAttributes frame]];
            
        }else{
            
            CGFloat w = rect.size.width-((SECTION_MARGIN_X*2)+HEADER_WIDTH+FOOTER_WIDTH+(PADDING_X*2));
            CGFloat h = self.itemSize.height;
            
            attributes.frame = CGRectMake(SECTION_MARGIN_X+HEADER_WIDTH+PADDING_X, attributes.frame.origin.y, w, h);
        }
    }

    return array;
}

-(UICollectionViewLayoutAttributes*)layoutAttributesForSupplementaryViewOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
    
    /*
        First get the attributes for the cell item
     */
    UICollectionViewLayoutAttributes* cellAttributes = [super layoutAttributesForItemAtIndexPath:indexPath];
    UICollectionViewLayoutAttributes* supViewAttributes;
    
    BOOL isHeader = [kind isEqualToString:UICollectionElementKindSectionHeader];
    
    /*
     We want our header view to align-left to the cell and the footer to sit on the right
     */
    supViewAttributes = [super layoutAttributesForSupplementaryViewOfKind:kind atIndexPath:indexPath];
    
    CGRect cellRect = [cellAttributes frame];
    
    if(isHeader){
        
        [supViewAttributes setFrame:CGRectMake(SECTION_MARGIN_X, cellRect.origin.y, HEADER_WIDTH, cellRect.size.height)];
        
    }else{
        
        CGRect collectionViewRect = self.collectionView.bounds;
        CGFloat footerXpos = collectionViewRect.size.width-(FOOTER_WIDTH+SECTION_MARGIN_X+PADDING_X);
        
        [supViewAttributes setFrame:CGRectMake(footerXpos, cellRect.origin.y, FOOTER_WIDTH, cellRect.size.height)];
    }
    
    return supViewAttributes;
}

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