Correct way to use UITableViewDataSource and Custom UITableViewCell Delegate - ios

Question

I'm working on moving the UITableViewDataSource outside of the UITableViewController. However I have some custom cells that have their own delegates, which then call on the tableView to reload.
I'm not sure what the correct way of handling this is. Here's what I have:
final class MyTableViewController: UITableViewController {
lazy var myTableViewDataSource: MyTableViewDataSource = { MyTableViewDataSource(myProperty: MyProperty) }()
override func viewDidLoad() {
super.viewDidLoad()
tableView.dataSource = myTableViewDataSource
}
}
Cell
protocol MyTableViewCellDelegate: AnyObject {
func doSomething(_ cell: MyTableViewCellDelegate, indexPath: IndexPath, text: String)
}
final class MyTableViewCell: UITableViewCell, UITextFieldDelegate {
#IBOutlet weak var packageSizeTextField: UITextField!
weak var delegate: MyTableViewCellDelegate?
var indexPath = IndexPath()
override func awakeFromNib() {
super.awakeFromNib()
}
func configureCell() {
// configureCell...
}
func textFieldDidChangeSelection(_ textField: UITextField) {
print(#function)
delegate?.doSomething(self, indexPath: indexPath, text: textField.text ?? "")
}
}
DataSource
final class MyTableViewDataSource: NSObject, UITableViewDataSource {
var myProperty: MyProperty!
init(myProperty: MyProperty) {
self.myProperty = myProperty
}
// ...
func doSomething(_ cell: MyTableViewCell, indexPath: IndexPath, text: String) {
// ...
tableView.performBatchUpdates({
tableView.reloadRows(at: [indexPath], with: .automatic)
})
// ERROR - tableView doesn't exist
}
}
My question is, how do I gain access to the tableView that this class is providing the source for? Is it as simple as adding a reference to the tableView like this?
var tableView: UITableView
var myProperty: MyProperty!
init(myProperty: MyProperty, tableView: UITableView) {
self.myProperty = myProperty
self.tableView = tableView
}

Answer 1

One option is to have your MyTableViewController conform to your MyTableViewCellDelegate and then set the controller as the delegate in cellForRowAt in your dataSource class.
However, you may be much better off using a closure.
Get rid of your delegate and indexPath properties in your cell, and add a closure property:
final class MyTableViewCell: UITableViewCell, UITextFieldDelegate {
#IBOutlet weak var packageSizeTextField: UITextField!
override func awakeFromNib() {
super.awakeFromNib()
configureCell()
}
func configureCell() {
// configureCell...
packageSizeTextField.delegate = self
}
var changeClosure: ((String, UITableViewCell)->())?
func textFieldDidChangeSelection(_ textField: UITextField) {
print(#function)
changeClosure?(textField.text ?? "", self)
// delegate?.doSomething(self, indexPath: indexPath, text: textField.text ?? "")
}
}
Now, in your dataSource class, set the closure:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let c = tableView.dequeueReusableCell(withIdentifier: "mtvc", for: indexPath) as! MyTableViewCell
c.packageSizeTextField.text = myData[indexPath.row]
c.changeClosure = { [weak self, weak tableView] str, c in
guard let self = self,
let tableView = tableView,
let pth = tableView.indexPath(for: c)
else {
return
}
// update our data
self.myData[pth.row] = str
// do something with the tableView
//tableView.reloadData()
}
return c
}
Note that as you have your code written, the first tap in the textField will not appear to do anything, because textFieldDidChangeSelection will be called immediately.
Edit
Here's a complete example that can be run without any Storyboard connections.
The cell creates a label and a text field, arranging them in a vertical stack view.
Row Zero will have the text field hidden and its label text will be set to the concatenated strings from myData.
The rest of the rows will have the label hidden.
The closure will be called on .editingChanged (instead of textFieldDidChangeSelection) so it is not called when editing begins.
Also implements row deletion for demonstration purposes.
The first row will be reloaded when text is changed in any row's text field, and when a row is deleted.
Cell Class
final class MyTableViewCell: UITableViewCell, UITextFieldDelegate {
var testLabel = UILabel()
var packageSizeTextField = UITextField()
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
super.init(style: style, reuseIdentifier: reuseIdentifier)
configureCell()
}
required init?(coder: NSCoder) {
super.init(coder: coder)
configureCell()
}
func configureCell() {
// configureCell...
let stack = UIStackView()
stack.axis = .vertical
stack.translatesAutoresizingMaskIntoConstraints = false
testLabel.numberOfLines = 0
testLabel.backgroundColor = .yellow
packageSizeTextField.borderStyle = .roundedRect
stack.addArrangedSubview(testLabel)
stack.addArrangedSubview(packageSizeTextField)
contentView.addSubview(stack)
let g = contentView.layoutMarginsGuide
NSLayoutConstraint.activate([
stack.topAnchor.constraint(equalTo: g.topAnchor),
stack.leadingAnchor.constraint(equalTo: g.leadingAnchor),
stack.trailingAnchor.constraint(equalTo: g.trailingAnchor),
stack.bottomAnchor.constraint(equalTo: g.bottomAnchor),
])
packageSizeTextField.addTarget(self, action: #selector(textChanged(_:)), for: .editingChanged)
}
var changeClosure: ((String, UITableViewCell)->())?
#objc func textChanged(_ v: UITextField) -> Void {
print(#function)
changeClosure?(v.text ?? "", self)
}
}
TableView Controller Class
class MyTableViewController: UITableViewController {
lazy var myTableViewDataSource: MyTableViewDataSource = {
MyTableViewDataSource()
}()
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .systemBackground
tableView.register(MyTableViewCell.self, forCellReuseIdentifier: "mtvc")
tableView.dataSource = myTableViewDataSource
}
}
TableView DataSource Class
final class MyTableViewDataSource: NSObject, UITableViewDataSource {
var myData: [String] = [
" ",
"One",
"Two",
"Three",
"Four",
"Five",
"Six",
"Seven",
"Eight",
]
func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
myData.remove(at: indexPath.row)
tableView.deleteRows(at: [indexPath], with: .fade)
tableView.reloadRows(at: [IndexPath(row: 0, section: 0)], with: .automatic)
} else if editingStyle == .insert {
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view.
}
}
func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
return indexPath.row != 0
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return myData.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let c = tableView.dequeueReusableCell(withIdentifier: "mtvc", for: indexPath) as! MyTableViewCell
c.testLabel.isHidden = indexPath.row != 0
c.packageSizeTextField.isHidden = indexPath.row == 0
if indexPath.row == 0 {
myData[0] = myData.dropFirst().joined(separator: " : ")
c.testLabel.text = myData[indexPath.row]
} else {
c.packageSizeTextField.text = myData[indexPath.row]
}
c.changeClosure = { [weak self, weak tableView] str, c in
guard let self = self,
let tableView = tableView,
let pth = tableView.indexPath(for: c)
else {
return
}
// update our data
self.myData[pth.row] = str
// do something with the tableView
// such as reload the first row (row Zero)
tableView.reloadRows(at: [IndexPath(row: 0, section: 0)], with: .automatic)
}
return c
}
}
Edit 2
There is a lot to discuss which goes beyond the scope of your question, but briefly...
First, as a general rule Classes should be as independent as possible.
your Cell should only handle its elements
your Data Source should only manage the data (and, of course, the necessary funds like returning cells, handling Edit commits, etc)
your TableViewController should, as might be expected, control the tableView
If you are only manipulating the data and wanting to reload specific rows, it's not that big of a deal for your DataSource class to get a reference to the tableView.
But, what if you need to do more than that? For example:
You don't want your Cell or DataSource class to act on the button tap and do something like pushing a new controller onto a nav stack.
To use the protocol / delegate pattern, you can "pass a delegate reference" through the classes.
Here's an example (with just minimum code)...
Two protocols - one for text change, one for button tap:
protocol MyTextChangeDelegate: AnyObject {
func cellTextChanged(_ cell: UITableViewCell)
}
protocol MyButtonTapDelegate: AnyObject {
func cellButtonTapped(_ cell: UITableViewCell)
}
The controller class, which conforms to MyButtonTapDelegate:
class TheTableViewController: UITableViewController, MyButtonTapDelegate {
lazy var myTableViewDataSource: TheTableViewDataSource = {
TheTableViewDataSource()
}()
override func viewDidLoad() {
super.viewDidLoad()
// assign custom delegate to dataSource instance
myTableViewDataSource.theButtonTapDelegate = self
tableView.dataSource = myTableViewDataSource
}
// delegate func
func cellButtonTapped(_ cell: UITableViewCell) {
// do something
}
}
The data source class, which conforms to MyTextChangeDelegate and has a reference to MyButtonTapDelegate to "pass to the cell":
final class TheTableViewDataSource: NSObject, UITableViewDataSource, MyTextChangeDelegate {
weak var theButtonTapDelegate: MyButtonTapDelegate?
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let c = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! theCell
// assign custom delegate to cell instance
c.theTextChangeDelegate = self
c.theButtonTapDelegate = self.theButtonTapDelegate
return c
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 10
}
func cellTextChanged(_ cell: UITableViewCell) {
// update the data
}
}
and the Cell class, which will call the MyTextChangeDelegate (the data source class) on text change, and the MyButtonTapDelegate (the controller class) when the button is tapped:
final class theCell: UITableViewCell, UITextFieldDelegate {
weak var theTextChangeDelegate: MyTextChangeDelegate?
weak var theButtonTapDelegate: MyButtonTapDelegate?
func textFieldDidChangeSelection(_ textField: UITextField) {
theTextChangeDelegate?.cellTextChanged(self)
}
func buttonTapped() {
theButtonTapDelegate?.cellButtonTapped(self)
}
}
So, having said all that...
Speaking in the abstract can be difficult. For your specific implementation, you may be digging yourself into a hole.
You mention "how to use a containerView / segmented control to switch between controllers" ... It might be better to create a "data manager" class, rather than a "Data Source" class.
Also, with a little searching for Swift Closure vs Delegate you can find a lot of discussion stating that Closures are the preferred approach these days.
I put a project up on GitHub showing the two methods. The functionality is identical --- one approach uses Closures and the other uses Protocol/Delegate pattern. You can take a look and dig through the code (tried to keep it straight-forward) to see which would work better for you.
https://github.com/DonMag/DelegatesAndClosures