Completion callback using closures in Swift

Asked May 09 '18 at 11:04

Active May 09 '18 at 11:50

Viewed 210 times

When I just going through with a library, there is an Internal property in a Singelton class. like this :-

class CameraHandler: NSObject, UIImagePickerControllerDelegate {

      static let shared = CameraHandler()

     //MARK: Internal Properties
     var imagePickedBlock: ((UIImage) -> Void)?   ///// What kind of property is THIS ???

     func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
       if let image = info[UIImagePickerControllerOriginalImage] as? UIImage {
           self.imagePickedBlock?(image)
       } else{
           print("Something went wrong")
       }
     }

 }

As you can see above imagePickedBlock variable changes when user selects an image. And also below function will fire. So my question is what type of Property is this? Thanks

CameraHandler.shared.imagePickedBlock = { (image) in
     /* get your image here */
     print("Got image!!!!")
}

edited May 09 '18 at 11:50

Arasuvel

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asked May 09 '18 at 11:04

Mudith Chathuranga Silva

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3

That's a closure. In Objective-C, it's called a block. – Larme May 09 '18 at 11:07
`var imagePickedBlock: ((UIImage) -> Void)?` stored Property of type closure with nill value so you needn't any initalizer for `CameraHandler ` – Abdelahad Darwish May 09 '18 at 11:09
1

You may refer to Swift document. https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html – Leo May 09 '18 at 11:12
Thanks @Leo and@Larme :) – Mudith Chathuranga Silva May 09 '18 at 11:13
1

That is string reference of closure as @Larme said. it will be executed whenever it will be triggered generally it is used for async task handling – Prashant Tukadiya May 09 '18 at 11:22

Completion callback using closures in Swift

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