GettingStartedWithCustomUICollectionViewLayouts-1

CustomLayout.m

-(void)prepareLayout
{
    //don't forget to call super here
    [super prepareLayout];
 
    /* pre-calculate and cache whatever you need here */
 
    //maybe you would want to loop over each cell like this?
    for(NSUInteger i = 0; i < [self.collectionView numberOfSections]; i++)
    {
        for(NSUInteger j = 0; j < [self.collectionView numberOfItemsInSection:i]; j++)
        {
            /* calculate something for the cell at row j in section i */
        }
    }
}