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iOS Build a Vending Machine App in Swift 2.0 Loading Data From a Resource Type Casting

Drew Carver
Drew Carver
5,189 Points
Posted by Drew Carver
Drew Carver
5,189 Points

How is it that NSObject is being downcast to a native type in Swift?

In the video, he says:

"NSObject is an Objective-C type that is the base class for every object in the language. Similarly, AnyObject represents any class in Swift. Because they both represent very high-level types, they can be downcast to a more concrete type to a subclass further down the tree."

This doesn't make sense because NSObject is not a base class in Swift. How can it be downcast to String? What am I missing?

1 Answer

Greg Kaleka
Greg Kaleka
39,021 Points
Greg Kaleka
Greg Kaleka
39,021 Points

Hi Drew,

Yep, you can totally downcast an NSObject to a Swift type. Hit up a playground and try it out yourself!

totallyValidCode.swift 
import Foundation

let nsTesting: NSObject = "Thingie"

let swiftyVersion: String = nsTesting as! String

This is because of the interoperability of Swift and Objective-C. I recommend checking out the Objective-C for Swift Developers course here on Treehouse, and/or the WWDC video Swift and Objective-C Interoperability from 2015.

Happy coding :beers:

-Greg