CODEWITHSUNDEEP
iosswift
Mani
Mani

Reputation: 17585

swift : equivalent to respondToSelector

I have searched and used 

UIDevice.currentDevice().instancesRespondToSelector(Selector("userInterfaceIdiom"))

But couldn't worked for me. Show error as

'UIDevice' doesn't have member named 'instancesRespondToSelector`

Also tried this 

UIDevice.instancesRespondToSelector(Selector("userInterfaceIdiom"))

But got error as

'UIDevice' doesn't have member named 'userInterfaceIdiom'

But UIDevice belongs to NSObject which have member instancesRespondToSelector? Please point out my mistake or suggest correct way to do it?

Upvotes: 1

Views: 1094

Answers (4)

rickster
rickster

Reputation: 126117

First, you don't need this particular selector check. The recommendation of calling [[UIDevice] currentDevice] userInterfaceIdiom] only after a respondsToSelector check dates back to iOS 3.x. At that time, iPhones running iOS 3.1 didn't have the userInterfaceIdiom method — only iPads running iOS 3.2 did.

Not only is nobody trying to support iOS 3.x anymore, you can't deploy to it with Swift. All versions of iOS that you can target from Xcode 6 (whether you code in Swift or ObjC) support calling userInterfaceIdiom, and for that matter, so do all versions you can target from Xcode 5.

Second, there's no need to write Selector("someSelectorName"). The Selector type adopts the StringLiteralConvertible protocol, so anywhere you see an API that takes a Selector, you can pass a string literal.

So, you can write either:

UIDevice.instancesRespondToSelector("userInterfaceIdiom")

or

UIDevice.currentDevice().respondsToSelector("userInterfaceIdiom")

But you shouldn't...

Finally, it's generally a bad idea to use userInterfaceIdiom to make layout decisions — for one thing, it leads to the wrong layout decisions whenever you want to use the same view controller both as a portrait-full-screen view on iPhone and as the master view in a split view on iPad.

In iOS 8, the preferred way for a view controller to adapt to the frame it's presented in is to use traits. In your view controller code, write something like this:

if self.traitCollection.horizontalSizeClass == .Compact {
    // lay out for iPhone portrait or iPad master-split / popover
} else {
    // lay out for iPad detail-split / fullscreen
}

You can get more info about designing adaptive view controllers in WWDC 2104 session 216: Building Adaptive Apps with UIKit.

Upvotes: 2

Alexey Sidorov
Alexey Sidorov

Reputation: 866

I think it should be like this:

UIDevice.userInterfaceIdiom?()

Upvotes: 0

Mani
Mani

Reputation: 17585

From @holex hint, I realize answer as

UIDevice.respondsToSelector(Selector("userInterfaceIdiom"))

Upvotes: 1

holex
holex

Reputation: 24041

the instancesRespondToSelector is still a class method and defintely not an instance method:

UIDevice.instancesRespondToSelector(Selector("userInterfaceIdiom"))

UPDATE#1

because the userInterfaceIdiom is a property of the instance only:

UIDevice.currentDevice().respondsToSelector(Selector("userInterfaceIdiom"))

Upvotes: 4

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