Objective C & Swift Interoperability causes error "Extensions may not contain stored properties"

Question

I was working on one of my previous app that was done on Objective C. I need to add a new module to it and I decided to use Swift for that particular module.

I have a class called HomePage in Objective C, I wanted to add some new IBActions and IBOutlets in it. For that I added a new swift file and extended the existing class like:

// MARK: IBOutlets and IBActions
extension HomePage
{
    @IBOutlet var image : UIImageView!
    ...

    /*!
    * Loads the application support webpage
    */
    @IBAction func loadSupportURL(sender : UIButton)
    {
    }
    ...
}

If I add only the IBActions everything is working perfectly. But when I add an IBOutlet, the compiler throws an error like:

Extensions may not contain stored properties

For fixing it I have two ways,

Declare the outlet in my Objective C class itself
Convert the whole Objective C class to Swift and declare the property there

Is there any other way to fix this issue ?

Yeah, as the compiler says, you cannot have stored properties in an extension, so you'd have to go with one of your solutions — Kametrixom, Jun 30 '15 at 11:13

score 7 · Accepted Answer · edited May 23 '17 at 12:00

As the error message clearly states, you can't have stored properties in an extension. But the thing is, you can't have them in Objective-C categories either, so the language isn't the problem here.

In both languages, you need to use associated references to implement stored properties. Please see this thread for an example of using associated references in Swift. Since it is a C API, its usage is pretty much the same in Objective-C.

Objective C & Swift Interoperability causes error "Extensions may not contain stored properties"

1 Answers1