Switching on UIButton title: Expression pattern of type 'String' cannot match values of type 'String?!'

Question

I'm trying to use a switch in an @IBAction method, which is hooked to multiple buttons

@IBAction func buttonClick(sender: AnyObject) {

        switch sender.currentTitle {
            case "Button1":
                print("Clicked Button1")
            case "Button2":
                print("Clicked Button2")
            default:
                break
        }

When I try the above, I get the following error:

Expression pattern of type 'String' cannot match values of type 'String?!'

@EdCottrell You can compare strings directly in Swift, since tests like `==` test for equality, while `===` tests if the objects are the same exact object. — NobodyNada, Apr 23 '16 at 17:48
@EdCottrell yep was using that before, for some reason I felt a switch would be cleaner, so tried to have a go. — Andrei, Apr 23 '16 at 17:49
`func buttonClick(sender: UIButton)` and `switch sender.currentTitle!` — Leo Dabus, Apr 23 '16 at 17:50
I would just add different tag values to them instead of reading their optional title — Leo Dabus, Apr 23 '16 at 17:51
@LeoDabus thanks for the comment, would love to know what are the pros/cons? — Andrei, Apr 23 '16 at 17:59
@LeoDabus Better to use named outlets than tags. Or separate action methods. — Sulthan, Apr 23 '16 at 18:00
If you are interested where the `!` in `String?!` comes from, have a look at http://stackoverflow.com/questions/33388830/the-strange-behaviour-of-swifts-anyobject. — Martin R, Apr 23 '16 at 18:01
@LeoDabus I do, I use that logic every day :) I only very dislike the usage of tags. — Sulthan, Apr 23 '16 at 18:06

Marc Khadpe · Accepted Answer · 2016-04-23T17:55:27.773

14

currentTitle is an optional so you need to unwrap it. Also, the type of sender should be UIButton since you are accessing the currentTitle property.

@IBAction func buttonClick(sender: UIButton) {
    if let theTitle = sender.currentTitle {
        switch theTitle {
            case "Button1":
                print("Clicked Button1")
            case "Button2":
                print("Clicked Button2")
            default:
                break
        }
    }
}

edited Apr 23 '16 at 17:55

answered Apr 23 '16 at 17:50

Marc Khadpe

2,012
16
14

Thanks for the answer, however I now get `Expression pattern of type 'String' cannot match values of type 'String?'` – Andrei Apr 23 '16 at 17:53
don't forget to mention also it only works because you changed the method parameter from AnyObject to UIButton – Leo Dabus Apr 23 '16 at 17:53
@Andrei Make sure to change the type of sender to `UIButton` – Marc Khadpe Apr 23 '16 at 17:57
@MarcKhadpe yep, missed that. Thanks. – Andrei Apr 23 '16 at 18:00
Why can't swift compare a `String` and a `String?` in a switch ? This looks stupid – Guig Oct 25 '16 at 20:46
3

@Guig Probably because optionals are actually enums, so it messes with the switch's logic. If you need to compare a non-optional to an optional switch, you can still do it by adding a ? to the end e.g. `case "Button1"?:` – John Montgomery Apr 05 '17 at 16:23
1

But you can compare them with `==` and switch is kind of the same thing right? – Guig Apr 05 '17 at 19:58

score 2 · Answer 2 · answered Oct 25 '17 at 13:47

2

Another way of unwrapping currentTitle and I think a more elegant one is:

switch sender.currentTitle ?? "" { 
    //case statements go here
}

answered Oct 25 '17 at 13:47

Vasil Garov

4,851
1
26
37

Switching on UIButton title: Expression pattern of type 'String' cannot match values of type 'String?!'

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