Products Google for Education Blockly Reference Blockly Framework Reference Item @objcMembers public class Item: NSObject Defines information on how each item should be laid out in the layout. rootBlock The root block for this item. Declaration Swift public fileprivate(set) var rootBlock: Block? gap The gap between the previous item and this one. Declaration Swift public fileprivate(set) var gap: CGFloat? Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see our Site Policies. Java is a registered trademark of Oracle and/or its affiliates. Last updated December 1, 2017.