Can't conform to obj-c protocol in Swift

Question

I'm creating an iOS app with Swift. I discovered an animation I'd like to implement in my table view, but the code is in Objective-C.

Repository: https://github.com/recruit-mp/RMPZoomTransitionAnimator

I have successfully bridged Obj-C code to Swift but can't seem to conform to a required protocol.

The protocol:

@protocol RMPZoomTransitionAnimating <NSObject> @required - (UIImageView *)transitionSourceImageView; - (UIColor *)transitionSourceBackgroundColor; - (CGRect)transitionDestinationImageViewFrame; @end

My Swift implementation:

First class that implements the protocol:

class ChallengeViewController: UIViewController, RMPZoomTransitionAnimating func transitionSourceImageView() -> UIImageView { return imageView } func transitionSourceBackgroundColor() -> UIColor { return UIColor.whiteColor() } func transitionDestinationImageViewFrame() -> CGRect { return imageView.frame }

Second class:

class ChallengeTableViewController: UITableViewController, RMPZoomTransitionAnimating func transitionSourceImageView() -> UIImageView { return imageForTransition! } func transitionSourceBackgroundColor() -> UIColor { return UIColor.whiteColor() } func transitionDestinationImageViewFrame() -> CGRect { return imageFrame! }

This check that occurs before animating always fails:

Protocol *animating = @protocol(RMPZoomTransitionAnimating); BOOL doesNotConfirmProtocol = ![self.sourceTransition conformsToProtocol:animating] || ![self.destinationTransition conformsToProtocol:animating];

I've read this topic How to create class methods that conform to a protocol shared between Swift and Objective-C? but didn't found any help

Any clues would be really appreciated

There is a sourceTransition and a destinationTransition. They are two different objects. They must both conform to RMPZoomTransitionAnimating. But you have only shown one object that conforms to RMPZoomTransitionAnimating. Where's the other one? — matt
– matt, Commented Oct 24, 2015 at 23:02
Possible duplicate of How to create class methods that conform to a protocol shared between Swift and Objective-C? — Jeef
– Jeef, Commented Oct 25, 2015 at 2:12
Okay, so what's your evidence that "This check that occurs before animating always fails"? You do conform to the protocol; if you didn't, the compiler would stop you and the code wouldn't even run. So what's the actual problem at this point? — matt
– matt, Commented Oct 25, 2015 at 14:33
Also - its possible you are going to have to use UnsafeMutalbePointers — Jeef
– Jeef, Commented Oct 25, 2015 at 16:11

Jeef · Accepted Answer · 2015-10-25 02:07:24Z

Swift classes by themselves are not (by default) Objective-C Compatible.

You get compatibility by either inheriting from NSObject or adding @objc in front of your class. I suspect this "may" be your issues - but I unfortunately can't test it at the moment.

You may also have to add a few initializers like in your case one from NSCoder or something - I don't unfortunately recall off the top of my head - and I don't have access to Xcode right now.

https://developer.apple.com/library/ios/documentation/Swift/Conceptual/BuildingCocoaApps/MixandMatch.html

Try:

@objc class ChallengeViewController: UIViewController, RMPZoomTransitionAnimating func transitionSourceImageView() -> UIImageView { return imageView } func transitionSourceBackgroundColor() -> UIColor { return UIColor.whiteColor() } func transitionDestinationImageViewFrame() -> CGRect { return imageView.frame }

This will tell the compiler your class is objective-c compatible

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