     let identifier = nibNameForObjectMatching(dataSource.objectAtIndexPath(indexPath)!)
     
     if let cell = instances[identifier] as? SizeCalculatingCell {
-      willCalculateSizeSignal.sendNext((instances[identifier]!, indexPath))
+      willCalculateSize.sendNext((instances[identifier]!, indexPath))
       return cell.sizeFor(dataSource.objectAtIndexPath(indexPath))
     }
     

  
  public var nibNameForObjectMatching: (ObjectType -> String)!
  
  public let didSelectCellSignal = Pipe<(cell: UICollectionViewCell?, object: ObjectType?)>()
  public let willDisplayCellSignal = Pipe<(UICollectionViewCell, NSIndexPath)>()
  public let willCalculateSizeSignal = Pipe<(UICollectionViewCell, NSIndexPath)>()
  public let didEndDisplayingCell = Pipe<(UICollectionViewCell, NSIndexPath)>()
  public let willSetObjectSignal = Pipe<(UICollectionViewCell, NSIndexPath)>()
  public let didSetObjectSignal = Pipe<(UICollectionViewCell, NSIndexPath)>()
  
  public var checkedIndexPaths = [NSIndexPath]() {
    didSet {

    identifiersForIndexPaths[indexPath] = identifier

    
    willSetObject.sendNext((cell, indexPath))
    let mapping = mappings[identifier]!
    mapping(object, cell, indexPath)
    didSetObject.sendNext((cell, indexPath))
    
    return cell
  }
