Removing views from superview in cell - ios

Question

I have a cell class 'NewsCell' (subclass of UITableViewCell) that I use for two different kinds of news: OrganizationNews and ProjectNews. These news has common things, but some of elements are different. Namely, when my cell is used for ProjectNews I want to hide Organization's logo, when it is for OrganizationNews I want to hide Project's name button.
I have 'configureCell(_, forNews, ofProject)' method. I call it in 'NewsViewController'. I used 'removeFromSuperview' method, because I need to rearrange my elements in 'NewsCell'. Changing 'isHidden' value won't give me that effect.
So, that is the issue. I have 'Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value' exception in the lines projectNameButton.removeFromSuperview() or logoImageView.removeFromSuperview().
What should I do?
// NewsViewController.swift
func configureCell(_ cell: NewsCell, forNews news: News, ofProject project: Project? = nil) {
//...
if news is OrganizationNews {
cell.projectNameButton.removeFromSuperview()
} else if news is ProjectNews {
cell.logoImageView.removeFromSuperview()
}
// ...
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let news = newsCollection[indexPath.row]
let cell = tableView.dequeueReusableCell(withIdentifier: TableViewCellIdentifiers.newsCell, for: indexPath) as! NewsCell
configureCell(cell, forNews: news)
cell.delegate = self
return cell
}

Answer 1

A UITableView or UICollectionView are built on the reuse concept, where the cells are reused and repopulated when you work on it.
When you try to call dequeReusableCell(withIdentifier:), it sometimes returns something that is created before. So, suppose you dequed before something which had all controls, then removed one (removeFromSuperview), then tried to deque again, the new dequed one may NOT have the subview.
I think the best solution for you is making two different cells.
Example:
class BaseNewsCell: UITableViewCell {
// Put the common views here
}
class OrganizationNewsCell: BaseNewsCell {
// Put here things that are ONLY for OrganizationNewsCell
}
class ProjectNewsCell: BaseNewsCell {
// Put here things that are ONLY for ProjectNewsCell
}
Then deque them from 2 different identifier by two different storyboard cells, xibs.
Or
class BaseNewsCell: UITableViewCell {
// Put the common views here
}
class OrganizationNewsCell: BaseNewsCell {
// This happens when this kind of cell is created for the first time
override func awakeFromNib() {
super.awakeFromNib()
someNonCommon.removeFromSuperview()
}
}
class ProjectNewsCell: BaseNewsCell {
override func awakeFromNib() {
super.awakeFromNib()
someOtherNonCommon.removeFromSuperview()
}
}
Note: This violates Liskov's principle (one of the SOLID principles), because you remove functionality from superclass in the subclass.

Answer 2

Change the removing lines as below,
if news is OrganizationNews {
cell.projectNameButton?.removeFromSuperview()
} else if news is ProjectNews {
cell.logoImageView?.removeFromSuperview()
}
This will fix the issue. But a good approach would be to create separate classes for each cell. You can create a base class to keep common logic there.

Answer 3

You shouldn't remove the subview from the outside of the cell. Let's refactor your code.
NewsCell.swift
final class NewsCell: UITableViewCell {
enum Kind {
case organization
case project
}
var logoImageView: UIImageView?
let nameLabel = UILabel()
var kind: NewsCell.Kind {
didSet {
if kind != oldValue {
setupLogoImageView()
self.setNeedsLayout()
}
}
}
init(kind: NewsCell.Kind, reuseIdentifier: String?) {
self.kind = kind
super.init(style: .default, reuseIdentifier: reuseIdentifier)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
// MARK: - Positioning
extension NewsCell {
override func layoutSubviews() {
super.layoutSubviews()
// Your layouting
switch kind {
case .organization:
// Setup frame for organization typed NewsCell
case .project:
// Setup frame for project typed NewsCell
}
}
}
// MARK: - Setup
extension NewsCell {
private func setupLogoImageView() {
logoImageView = kind == .organization ? UIImageView() : nil
}
}
How to use:
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let news = newsCollection[indexPath.row]
var cell = tableView.dequeueReusableCell(withIdentifier: TableViewCellIdentifiers.newsCell) as? NewsCell
if cell == nil {
cell = NewsCell(kind: .organization, reuseIdentifier: TableViewCellIdentifiers.newsCell)
}
cell!.kind = news is Organization ? .organization: .project
return cell!
}