Linking multiple custom UITableViewCell's to single xib - ios

Question

Question
I'm creating a re-usable custom UITableViewCell and then subclassing it for re-use. How do I set these various subclasses to link to the same xib file?
Background
Let's call my custom UITableViewCell PickerTableViewCell. This cell includes a UIPickerView, as well as all the implementations as to how the picker view looks and behaves. When I want to use this cell, the only thing I need to give it is the data for the picker view. So I subclass PickerTableViewCell, then simply create the data source I need and assign it to the picker view. So far this has all worked well.
Here are the relevant parts of PickerTableViewCell:
class PickerTableViewCell: UITableViewCell {
var picker: UIPickerView! = UIPickerView()
var pickerDataSource: PickerViewDataSource!
override func awakeFromNib() {
super.awakeFromNib()
self.picker = UIPickerView(frame: CGRect(x: 0, y: 40, width: 0, height: 0))
self.picker.delegate = self
self.assignPickerDataSource()
}
// Must be overriden by child classes
func assignPickerDataSource() {
fatalError("Must Override")
}
Here is an example of a subclass:
class LocationPickerTableViewCell: PickerTableViewCell {
override func assignPickerDataSource() {
self.pickerDataSource = LocationPickerDataSource()
self.picker.dataSource = self.pickerDataSource
}
}
Problem
Since I am using these cells all over the place, with different data sources, I created a xib file which defines how the cell looks called PickerTableViewCell.xib, and assign it to the class PickerTableViewCell. In the view controllers I want to use it for, I register the cell with the table view inside viewDidLoad(). Then, inside func tableView(_:, cellForRowAt) I dequeue the subclass I want like this:
let cell = tableView.dequeueReusableCell(withIdentifier: "reuseIdentifier") as! LocationPickerTableViewCell
return cell
This is where the problem happens. The cell that is created is a PickerTableViewCell, not its subclass LocationPickerTableViewCell. This runs into the fatal error I placed in the parent class which is overriden by the child class.
The only way I have found to solve this is to create a separate xib file for each subclass I want to create, and assign it to the relevant subclass. While this solution does work, it feels wrong to have all of these xib files which are practically identical (except for which class they are assigned to) inside my project.
Is there a way I can overcome this problem, and have all of these cells link to the same single xib file?
Thanks! :)

Answer 1

Add view loaded by xib to UITableViewCell classes in which you want to use it.
Create your xib as per your require design, in your example PickerTableViewCell.xib
Create UITableViewCell sub-classes in which you want to use that view. I am using FirstTableViewCell & SecondTableViewCell for this.
in constructor of table cell load the xib and add it to table cell.
let nib = Bundle.main.loadNibNamed("PickerTableViewCell", owner: nil, options: nil)
if let view = nib?.first as? UIView{
self.addSubview(view)
}
if xib have any #IBOutlet then get them by viewWithTag function and assign to class variables
if let label = self.viewWithTag(1) as? UILabel{
self.label = label
}
override reuseIdentifier var of each tableviewCell subclass with different name
override var reuseIdentifier: String?{
return "FirstTableViewCell"
}
Now You can use these classes where you want, for using this follow below steps:
register this tableviewCell subclass with xib with tableview:
tableView.register(FirstTableViewCell.self, forCellReuseIdentifier:"PickerTableViewCell")
now in cellForRowAt indexPath method use it.
var cell = tableView.dequeueReusableCell(withIdentifier: "FirstTableViewCell", for: indexPath) as? FirstTableViewCell
if cell == nil {
cell = FirstTableViewCell()
}
cell?.label?.text = "FirstTableViewCell"

Answer 2

Don't use subclassing to assign different data sources.
Approach 1: Assign pickerDataSource in tableView(_:cellForRowAt:)
In the table view controller, you need to assign pickerDataSource
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "reuseIdentifier") as! PickerTableViewCell
cell.pickerDataSource = LocationPickerDataSource()
return cell
}
Handle additional work needed after the assignment of pickerDataSource with a didSet.
class PickerTableViewCell: UITableViewCell {
var picker: UIPickerView! = UIPickerView()
var pickerDataSource: PickerViewDataSource! {
didSet {
self.picker.dataSource = self.pickerDataSource
}
}
…
}
Approach 2: Extend PickerTableViewCell in all the needed ways.
Here instead of subclassing add the needed logic to a uniquely named setup method each defined in their own extension.
extension PickerTableViewCell {
func setupLocationPickerDataSource() {
self.pickerDataSource = LocationPickerDataSource()
self.picker.dataSource = self.pickerDataSource
}
}
then in tableView(_:cellForRowAt:)
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "reuseIdentifier") as! PickerTableViewCell
cell.setupLocationPickerDataSource()
return cell
}