Nil while unwrapping an Optional IBOutlet value

Question

I have got a fatal error: unexpectedly found nil while unwrapping an Optional value for an IBOutlet.

In my custom view, I have associated my outlet with a XIB file. I have double checked this. This is how it looks like:

@IBOutlet weak var label: UILabel! {
    didSet {
        label.textColor = .redColor()
    }
}

My implementation of layoutSubviews looks like:

override func layoutSubviews() {
    super.layoutSubviews()

    label.preferredMaxLayoutWidth = label.frame.size.width
}

Despite the fact, that layoutSubviews method has to be called after UI elements initialisation, I get an error:

fatal error: unexpectedly found nil while unwrapping an Optional value

This error is triggered by line:

label.preferredMaxLayoutWidth = label.frame.size.width

Why is that so? How to fix it?

Maybe the link between storyboard and your file is broken, try to create a new link (ctrl + drag) to your IBoutlet — Arnaud Wurmel, Nov 03 '16 at 09:00
maybe `@IBOutlet weak var label: UILabel? = nil { didSet { label?.textColor = .redColor() } }`, etc... — holex, Nov 08 '16 at 17:01

score 1 · Answer 1 · edited Dec 01 '17 at 18:36

1

You can prevent the crash from happening by safely unwrapping label with an if let statement.

if let mylabel = label {
   mylabel.preferredMaxLayoutWidth = mylabel.frame.size.width
}

edited Dec 01 '17 at 18:36

Forge

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answered Nov 03 '16 at 09:05

Nyakiba

862
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Yes, but for me it is interesting, why label is not ready? Also, where is the guarantee, that `preferredMaxLayoutWidth` will be setup? – Daumantas Versockas Nov 03 '16 at 09:32
read this: http://stackoverflow.com/questions/7588066/loading-custom-uiview-from-nib-all-subviews-contained-in-nib-are-nil – iGenio Nov 18 '16 at 11:23

iGenio · Answer 2 · 2016-11-08T16:51:48.570

1

You should use:

label?.preferredMaxLayoutWidth = label.frame.size.width

This before in an early call of layoutSubviews the outlet could not be yet setted, but in the next call will be. Using otional chaining you can avoid explicit optional unwrapping. if label is nil the assignment is skipped automatically.

edited Nov 08 '16 at 16:51

answered Nov 08 '16 at 16:42

iGenio

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dirtydanee · Accepted Answer · 2016-11-03T09:41:24.270

0

Try doing it in viewDidLayoutSubviews instead of layoutSubviews. You UI elements should be ready in viewDidLayoutSubviews, but not necessary in layoutSubviews.

edited Nov 03 '16 at 09:41

answered Nov 03 '16 at 09:03

dirtydanee

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Yea, but the problem is, that this is a view, not a view controller – Daumantas Versockas Nov 03 '16 at 09:29
`awakeFromNib()` ? – dirtydanee Nov 03 '16 at 09:37
This method doesn't fit well for me. – Daumantas Versockas Nov 03 '16 at 09:39
may i ask why? But than, in the viewController, in what you present your uiview, set the label preferedwidth in that `viewDidLayoutSubviews` call. – dirtydanee Nov 03 '16 at 09:41
I am implementing hack to enable dynamic table view cells for iOS 7. I need to set this property after layout changes. – Daumantas Versockas Nov 03 '16 at 09:43
Dude, why are you still developing for iOS 7? Probably it is not your decision, but have you checked the latest usage stats for iOS 7?? – dirtydanee Nov 03 '16 at 09:53
Trust me, pal, if it is up to me, I wold have been dropped iOS 7 support long time ago :). – Daumantas Versockas Nov 03 '16 at 09:59
yeah i guess so! So trying to call the viewController's `viewDidLayoutSubviews` function? Just reference the UIView in your viewController, and do it from there? – dirtydanee Nov 03 '16 at 10:01
In this case I would have to expose my 'UIView' properties. I would like to keep them private. Also, this doesn't sounds right. But I agree, it should work. – Daumantas Versockas Nov 03 '16 at 10:04
you have to expose the `UIView`, but you could keep the properties private, and set the width with a public function. – dirtydanee Nov 03 '16 at 10:18

Nil while unwrapping an Optional IBOutlet value

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