Revision control
Copy as Markdown
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
import UIKit
/// A protocol for any object to inherit the `cellIdentifier` string property.
///
/// Intended for use with views that must register/deque cells, this allows
/// a cleaner implementation of the cell identifier by bypassing it being
/// hardcoded which is prone to error.
///
/// As defined in the extensions, this will generally, where adhering to the
/// implemented conditions, return a string describing `self`.
public protocol ReusableCell: AnyObject {
static var cellIdentifier: String { get }
}
public extension ReusableCell where Self: UICollectionViewCell {
static var cellIdentifier: String { return String(describing: self) }
}
public extension ReusableCell where Self: UITableViewCell {
static var cellIdentifier: String { return String(describing: self) }
}
public extension ReusableCell where Self: UITableViewHeaderFooterView {
static var cellIdentifier: String { return String(describing: self) }
}
public extension ReusableCell where Self: UICollectionReusableView {
static var cellIdentifier: String { return String(describing: self) }
}
public extension UICollectionView {
func dequeueReusableCell<T: ReusableCell>(cellType: T.Type, for indexPath: IndexPath) -> T? {
guard let cell = dequeueReusableCell(withReuseIdentifier: T.cellIdentifier, for: indexPath) as? T
else { return nil }
return cell
}
func dequeueSupplementary<T: ReusableCell>(of kind: String, cellType: T.Type, for indexPath: IndexPath) -> T? {
guard let cell = dequeueReusableSupplementaryView(
ofKind: kind,
withReuseIdentifier: T.cellIdentifier,
for: indexPath) as? T
else { return nil }
return cell
}
func registerSupplementary<T: ReusableCell>(of kind: String, cellType: T.Type) {
register(T.self, forSupplementaryViewOfKind: kind, withReuseIdentifier: T.cellIdentifier)
}
func register<T: ReusableCell>(cellType: T.Type) {
register(T.self, forCellWithReuseIdentifier: T.cellIdentifier)
}
/// Returns `true` if the `indexPath` is not out of bounds.
func isValid(indexPath: IndexPath) -> Bool {
return 0..<numberOfSections ~= indexPath.section
&& 0..<numberOfItems(inSection: indexPath.section) ~= indexPath.row
}
/// Returns the list of UICollectionViewCells which are fully visible within the UICollectionView's bounds.
/// Note: This list will be empty if there are pending layout updates.
var fullyVisibleCells: [UICollectionViewCell] {
return visibleCells.filter({ self.bounds.contains($0.frame) })
}
/// Returns the list of cell IndexPaths which are fully visible within the UICollectionView's bounds.
/// Note: This list will be empty if there are pending layout updates.
var indexPathsForFullyVisibleItems: [IndexPath] {
return fullyVisibleCells.compactMap({ indexPath(for: $0) })
}
}
public extension UITableView {
func register<T: ReusableCell>(cellType: T.Type) {
register(T.self, forCellReuseIdentifier: T.cellIdentifier)
}
func registerHeaderFooter<T: ReusableCell>(cellType: T.Type) {
register(T.self, forHeaderFooterViewReuseIdentifier: T.cellIdentifier)
}
}