IGListKit/Examples/Examples-iOS/IGListKitExamples/SectionControllers/GridSectionController.swift

/*
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import IGListKit
import IGListSwiftKit
import UIKit

final class GridItem: NSObject {

    let color: UIColor
    let itemCount: Int

    var items: [String] = []

    init(color: UIColor, itemCount: Int) {
        self.color = color
        self.itemCount = itemCount

        super.init()

        self.items = computeItems()
    }

    private func computeItems() -> [String] {
        return [Int](1...itemCount).map {
            String(describing: $0)
        }
    }
}

extension GridItem: ListDiffable {

    func diffIdentifier() -> NSObjectProtocol {
        return self
    }

    func isEqual(toDiffableObject object: ListDiffable?) -> Bool {
        return self === object ? true : self.isEqual(object)
    }

}

final class GridSectionController: ListSectionController {

    private var object: GridItem?
    private let isReorderable: Bool

    required init(isReorderable: Bool = false) {
        self.isReorderable = isReorderable
        super.init()
        self.minimumInteritemSpacing = 1
        self.minimumLineSpacing = 1
    }

    override func numberOfItems() -> Int {
        return object?.itemCount ?? 0
    }

    override func sizeForItem(at index: Int) -> CGSize {
        let width = collectionContext?.containerSize.width ?? 0
        let itemSize = floor(width / 4)
        return CGSize(width: itemSize, height: itemSize)
    }

    override func cellForItem(at index: Int) -> UICollectionViewCell {
        let cell: CenterLabelCell = collectionContext.dequeueReusableCell(for: self, at: index)
        cell.text = object?.items[index] ?? "undefined"
        cell.backgroundColor = object?.color
        return cell
    }

    override func didUpdate(to object: Any) {
        self.object = object as? GridItem
    }

    override func canMoveItem(at index: Int) -> Bool {
        return isReorderable
    }

    override func moveObject(from sourceIndex: Int, to destinationIndex: Int) {
        guard let object = object else { return }
        let item = object.items.remove(at: sourceIndex)
        object.items.insert(item, at: destinationIndex)
    }
}