CODEWITHSUNDEEP
swiftoption-typeoptional-binding
Boon
Boon

Reputation: 41480

How do you perform optional binding on an optional of optional?

How do you do optional binding on an optional of optional?

For example, assume UIViewController's navigationController property is an optional of optional. Should I use method #1 or method #2, or is there a third way?

Method #1

if let navigationController = viewController.navigationController! {

}

or

Method #2

if let optionalNavigationController = viewController.navigationController {
   let navigationController = optionalNavigationController {

    }
}

Upvotes: 1

Views: 87

Answers (4)

vadian
vadian

Reputation: 285082

If you know that the view controller has a navigation controller, because you designed it in Interface Builder or created it programmatically, declare a variable

var navigationController : UINavigationController!

and assign the navigation controller in viewDidLoad() as implicit unwrapped optional

navigationController = viewController!.navigationController!

If you don't know, use a normal optional binding as described in the other answers

Upvotes: 0

rshev
rshev

Reputation: 4176

Much more functional-programming solution:

if let a = optionalOfOptional?.map({$0}) {
    println(a)
}

Upvotes: 0

oisdk
oisdk

Reputation: 10091

if let navigationController = viewController?.navigationController

Upvotes: 0

Dániel Nagy
Dániel Nagy

Reputation: 12015

There is another solution:

if let stillOptional = viewController.navigationController, let notOptional = stillOptional {
    //use notOptional here
}

Upvotes: 1

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