CODEWITHSUNDEEP
swift
jatrp5
jatrp5

Reputation: 31

Swift: ! instead of = nil

I've recently taken up Swift in order to learn how to program iOS apps. I've been following Skip Wilson's tutorials and there's a moment when he connects an outlet and gets:

@IBOutlet var ticTacImg1: UIImageView = nil

instead of getting that I obtain:

@IBOutlet var ticTacImg1: UIImageView!

if I try to change it Xcode tells me it's an error. What am I doing wrong?

Upvotes: 1

Views: 89

Answers (2)

nickgraef
nickgraef

Reputation: 2417

@IBOutlet var ticTacImg1: UIImageView! is the correct code.

An @IBOutlet property needs to be optional because it initially has a nil value before the system connects the view to it. Marking it as an implicitly unwrapped optional with ! means that it will be unwrapped automatically whenever it is used.

I'm not sure which specific tutorial you're referencing, but my initial thought is that he could be using an early beta of Xcode 6 that didn't enforce this.

Upvotes: 1

Jeffery Thomas
Jeffery Thomas

Reputation: 42598

In early versions of Xcode 6, anything marked as @IBOutlet was turned into a weak implicitly unwrapped optional.

That is

@IBOutlet var ticTacImg1: UIImageView = nil

would be compiled as

@IBOutlet weak var ticTacImg1: UIImageView! = nil

This is no longer true. Now you must declare its optional status, but it will still be weak.

That is

@IBOutlet var ticTacImg1: UIImageView! = nil

would be compiled as

@IBOutlet weak var ticTacImg1: UIImageView! = nil

The reason why ticTacImg1 is not initialized to nil is that it doesn't matter. In Swift, implicitly unwrapped optionals which are not initialized have the value nil, so = nil is redundant.

Upvotes: 3

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