Delegation not working Swift

Question

I'm trying to implement the delegation pattern on Swift. The process consists in a popover that is displayed from a UIMenuItem in a text selection on a textView. This popover is a TableViewController that contains some colors. When a cell (or color) is tapped, the selected text changes its color from black to the selected color. I have the following protocol in the sending class:

protocol SelectedColorDelegate {
func didSelectColorCell(color: UIColor)
}

Then in the sending class I created this property:

var colorCellDelegate: SelectedColorDelegate?

In the method didSelectRowAtIndexPath of the tableViewController (popover) that is the sending class, I assigned the required parameter:

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let color = arrayOfColorValues[indexPath.row]
    self.colorCellDelegate?.didSelectColorCell(color: color)
}

In my receiving class that is a ViewController I set the protocol SelectedColorDelegate, and conformed to it with this method, aimed to change the textColor:

func didSelectColorCell(color: UIColor) {
    let textRange = noteTextView.selectedRange
    let string = NSMutableAttributedString(attributedString: noteTextView.attributedText)
    string.addAttribute(NSForegroundColorAttributeName, value: color, range: textRange)
    noteTextView.attributedText = string
    noteTextView.selectedRange = textRange
}

But the last method is never called, tapping the cell of the popover does nothing, what am I missing or doing wrong? Thanks!! :)

can you put breakpoint in function with `didSelectRowAt` and check if it colled? — Adrian Bobrowski, Dec 23 '16 at 06:19
popover?.delegate = self ; make sure you assign these delegate to the Viewcontroller. — Himanshu, Dec 23 '16 at 06:29
@MarilynGarcía ok then now print `self.colorCellDelegate` in function with `didSelectRowAt` i think this delegate is nil — Adrian Bobrowski, Dec 23 '16 at 06:38
@AdrianBobrowski yep, it is nil, how can I assign it to theViewController? I'm a beginner hahaha — Marilyn García, Dec 23 '16 at 06:43

Adrian Bobrowski · Accepted Answer · 2016-12-24T06:40:55.140

7

First of all define your protocol as only for classes

protocol SelectedColorDelegate: class {
    func didSelectColorCell(color: UIColor)
}

Secondly we want our delegate to be weakly retained

weak var colorCellDelegate: SelectedColorDelegate?

Finally set delegate when you show other view or in viewDidLoad eg:

class YourViewController: SelectedColorDelegate {
    final override func viewDidLoad() {
        super.viewDidLoad()

        self.colorCellDelegate = self
    }
}

Tutorial - How To Make Weak Delegates In Swift

edited Dec 24 '16 at 06:40

answered Dec 23 '16 at 07:09

Adrian Bobrowski

2,681
1
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I managed to find my mistake, but if I set the delegate as a weak reference the compiler complains, saying that "weak may only be applied to class and class-bound protocol types", not the simple protocol that I implemented, so my protocol has to be a class-only type. Thanks! – Marilyn García Dec 24 '16 at 04:48
@MarilynGarcía define your protocol as only for classes. Look for my edited answer – Adrian Bobrowski Dec 24 '16 at 06:42

score 1 · Answer 2 · answered Dec 23 '16 at 07:08

In PopOverTableViewController, setup should look like -

class PopOverTableViewController: UITableViewController, SelectedColorDelegate {

    override func viewDidLoad() {
          super.viewDidLoad()
          self.colorCellDelegate = self
    }
}

score 0 · Answer 3 · answered Dec 23 '16 at 06:29

0

Did you do: xxTableViewController.colorCellDelegate = self in xxViewController?

And your delegate declaration should be weak:

weak var colorCellDelegate: SelectedColorDelegate?

answered Dec 23 '16 at 06:29

Yun CHEN

6,450
3
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Does the asisgnment of the ViewController to the colorCellDelegate go in the viewDidLoad()? – Marilyn García Dec 23 '16 at 06:38
@MarilynGarcía, where you create the xxTableViewController: let xxTableViewController = XXTableViewController(); xxTableViewController.colorCellDelegate = self – Yun CHEN Dec 23 '16 at 06:43

Delegation not working Swift

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