CODEWITHSUNDEEP
iosswiftgenerics
ixx
ixx

Reputation: 32273

Generics not working with implicitly unwrapped optional

I created an extension of UIView to be able to create and add a subview in one line:

extension UIView {

    func createAndAddSubview<T:UIView>() -> T {
        let view = T()
        self.addSubview(view)
        return view
    }
}

This works with normal declarations:

let myLabel:UILabel = view.createAndAddSubview()
var myImageView:UIImageView = view.createAndAddSubview()

But with implicitly wrapped optionals I get a compiler error. I think it's because the optional prevents the compiler from determining the correct type.

'UIView' is not convertible to 'UILabel'

class MyController {
    var myLabel:UIlabel!

    func foo() {
        myLabel = view.createAndAddSubview()
    }
}

Of course I can get it to work like this

let myLabel:UILabel = view.createAndAddSubview()
self.myLabel = myLabel

But this isn't one line anymore... how can I improve it?

Thanks!

Upvotes: 0

Views: 165

Answers (1)

Kirsteins
Kirsteins

Reputation: 27335

I guess compiler cannot infer the type as its ImplicitlyUnwrappedOptional. Try:

self.myLabel = .Some(self.view.createAndAddSubview())

or

extension UIView {
    func createAndAddSubview<T:UIView>() -> T? {
        let view = T()
        self.addSubview(view)
        return view
    }
}

Upvotes: 1

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