How can I add protocol to an element from interfacebuilder in Swift?

Question

If I have an instance of UILabel in storyboard and I have it connected to view controller as IBOutlet. If I want add some functionality only to this label, how can I do it? I know that for obj-c you make a subclass of UILabel. But I wonder if there is better approach in swift.

Is it possible for this specific label to conform to some protocol that I'll make.

If you want to conform any protocol, you need to subclass this `UILabel` or create extension in needed scope in your application — Artem Novichkov, Nov 21 '16 at 10:00
ok, so I think the extension is the way. Can configure extenstion just for one label? — Klemen, Nov 21 '16 at 11:05

Luca D'Alberti · Accepted Answer · 2016-11-21T11:17:22.757

2

You can declare a private extension in the same file you're using the UILabel

private extension UILabel {}

In this case only the components in the same file can use the new feature. I know, it's a kind of workaround, but in my cases where I create a single file per each component, it works.

Pay attention that the protocol conformance has to be public, so you can't use the private access level

EDIT: since you need a special configuration for only one UILabel in a single file, this way won't allow it. Subclassing is the only solution

edited Nov 21 '16 at 11:17

answered Nov 21 '16 at 11:07

Luca D'Alberti

4,749
3
25
45

ok if I declare multiple labels inside a view controller, then this private extension will still effects all the labels. Thanks for helping me – Klemen Nov 21 '16 at 11:11
1

Then subclassing is the only solution @KlemenZagar – Luca D'Alberti Nov 21 '16 at 11:12
ok, just put this explanation at the end of your answer and I'' mark it as an accepted solution. – Klemen Nov 21 '16 at 11:16
did it @KlemenZagar. Hope it helped – Luca D'Alberti Nov 21 '16 at 11:17

shallowThought · Answer 2 · 2016-11-21T11:03:59.530

0

If I want add some functionality only to this label, how can I do it?

you can add functionality to an existing class using extensions:

extension UILabel {
    func foo() -> String{
        // this funtionality is availible on all UILabels now. 
        // You can also call self. Example:
        return self.text
    }
}

Find detailed information here.

edited Nov 21 '16 at 11:03

answered Nov 21 '16 at 11:02

shallowThought

19,212
9
65
112

ok, but what if a dont want this to be part of all the labels on the screen? – Klemen Nov 21 '16 at 11:03
Than you have to subclass `UILabel` and use your custom class. – shallowThought Nov 21 '16 at 11:05

How can I add protocol to an element from interfacebuilder in Swift?

2 Answers2