How to keep an object's reference when using UITableView? - swift

Question

The problem I'm facing is probably some lack of understanding on the concept of reusable cells. I have, let's say, 30 rows to be created and each of them has a UISwitch.
When I toggle one of the switches, it's behavior should affect the other 29. The point is: as far as I know, iOS doesn't create all of them at once, but rather wait to reuse the cells when the TableView is scrolled up and down.
How can I keep a copy of those reused objects and tell iOS to set the proper value to the switches?
I've thought on having the cells appended to a [UISwitch] but I can't manage to have all the 30 cells in there, look:
...
var switches = [UISwitch]()
...
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Field10Cell", for: indexPath) as! Field10TableViewCell
...
//cell.value is a UISwitch
if !switches.contains(cell.value) {
switches.append(cell.value)
}
return cell
}

Answer 1

You could create a set which stores the indexes of the cells whose switches have been pressed.
var activeSwitches = Set<IndexPath>()
Whenever a user presses the switch on a cell, you store it on the set like this:
activeSwitches.insert(indexPath)
If you need to check if a switch was activated, just check if its container cell's indexPath is in active switches like so:
if activeSwitches.contains(indexPath) {
// do something
}
In order to know when a user pressed a specific switch I recommend the folliwing:
In cellForRowAtIndexPath save the current indexPath into your Field10TableViewCell.
Create a protocol on Field10TableViewCell and add a delegate.
protocol Field10Delegate {
func didChangeSwitch(value: Bool, indexPath: IndexPath)
}
class Field10TableViewCell {
var delegate: Field10Delegate?
var indexPath: IndexPath?
#IBOutlet weak var fieldSwitch: UISwitch! // Can't use 'switch' as a variable name
#IBAction func switchValueChanged(_ sender: UISwitch) {
if let indexPath = indexPath {
delegate?.didChangeSwitch(value: sender.isOn, indexPath: indexPath)
}
}
When you create a cell, set the view controller as a delegate
let cell = tableView.dequeueReusableCell(withIdentifier: "Field10Cell", for: indexPath) as! Field10TableViewCell
cell.delegate = self
cell.indexPath = indexPath
Make your view controller comply with the protocol:
extension ViewController: Field10Delegate {
/* Whenever a switch is pressed on any cell, this delegate will
be called. This is a good place also to trigger a update to
your UI if it has to respond to switch changes.
*/
func didChangeSwitch(value: Bool, indexPath: IndexPath) {
if value {
activeSwitches.insert(indexPath)
} else {
activeSwitches.remove(indexPath)
}
updateUI()
}
}
With the above, at any point you will know which switches are active or not and you can process the dequeued cells with this information.