Objective-C protocol in Swift - shows does not conform error

Question

I am trying use an Objective-C library (MWPhotoBrowser) in my Swift app. My Swift class conforms to MWPhotoBrowserDelegate protocol by implementing required methods. However, I keep getting the following error:

"Type 'PhotoLibrary' does not conform to protocol 'MWPhotoBrowserDelegate'"

Cocoa protocols seem to work fine. Has anyone encountered this issue before?

Here is the sample code:

class PhotoLibrary: UIImageView, MWPhotoBrowserDelegate {

    init() {
        super.init(frame: CGRectZero)
    }

    func numberOfPhotosInPhotoBrowser(photoBrowser: MWPhotoBrowser!) -> Int {
        return 0
    }

    func photoBrowser(photoBrowser: MWPhotoBrowser!, photoAtIndex index: Int) -> MWPhoto! {
        return nil
    }
}

Protocol definition is as follows:

@protocol MWPhotoBrowserDelegate <NSObject>

- (NSInteger)numberOfPhotosInPhotoBrowser:(MWPhotoBrowser *)photoBrowser;
- (id <MWPhoto>)photoBrowser:(MWPhotoBrowser *)photoBrowser photoAtIndex:(NSInteger)index;

@optional

- (id <MWPhoto>)photoBrowser:(MWPhotoBrowser *)photoBrowser thumbPhotoAtIndex:(NSUInteger)index;
- (MWCaptionView *)photoBrowser:(MWPhotoBrowser *)photoBrowser captionViewForPhotoAtIndex:(NSUInteger)index;
- (NSString *)photoBrowser:(MWPhotoBrowser *)photoBrowser titleForPhotoAtIndex:(NSUInteger)index;
- (void)photoBrowser:(MWPhotoBrowser *)photoBrowser didDisplayPhotoAtIndex:(NSUInteger)index;
- (void)photoBrowser:(MWPhotoBrowser *)photoBrowser actionButtonPressedForPhotoAtIndex:(NSUInteger)index;
- (BOOL)photoBrowser:(MWPhotoBrowser *)photoBrowser isPhotoSelectedAtIndex:(NSUInteger)index;
- (void)photoBrowser:(MWPhotoBrowser *)photoBrowser photoAtIndex:(NSUInteger)index selectedChanged:(BOOL)selected;
- (void)photoBrowserDidFinishModalPresentation:(MWPhotoBrowser *)photoBrowser;

@end

Answer 1

I got MWPhotoBrowser working in my Swift app with the following code without needing to change the MWPhotoBrowser codebase.

func showFullScreenImage(image:UIImage) {
    let photo:MWPhoto = MWPhoto(image:image)

    self.photos = [photo]

    let browser:MWPhotoBrowser = MWPhotoBrowser(delegate: self)

    browser.displayActionButton = true
    browser.displayNavArrows = false
    browser.displaySelectionButtons = false
    browser.zoomPhotosToFill = true
    browser.alwaysShowControls = false
    browser.enableGrid = false
    browser.startOnGrid = false
    browser.enableSwipeToDismiss = true

    browser.setCurrentPhotoIndex(0)

    self.navigationController?.pushViewController(browser, animated: true)
}

func numberOfPhotosInPhotoBrowser(photoBrowser: MWPhotoBrowser!) -> UInt {
    return UInt(self.photos.count)
}

func photoBrowser(photoBrowser: MWPhotoBrowser!, photoAtIndex index: UInt) -> MWPhotoProtocol! {
    if Int(index) < self.photos.count {
        return photos.objectAtIndex(Int(index)) as! MWPhoto
    }
    return nil
}

func photoBrowserDidFinishModalPresentation(photoBrowser:MWPhotoBrowser) {
    self.dismissViewControllerAnimated(true, completion:nil)
}

I set photos as a class var, eg private var photos = [] , and added the following imports in my app's Bridging-Header.h file:

#import <MWPhotoBrowser/MWPhoto.h>
#import <MWPhotoBrowser/MWPhotoBrowser.h>

I got most of the above code from https://github.com/mwaterfall/MWPhotoBrowser/issues/325#issuecomment-64781477 .

Answer 2

Here's what I figured out:

Swift has issues with id data type. I had to modify MWPhotoBrowser code to replace all instances of id to (MWPhoto *). I think MWPhoto * should have been used in the first place.

That fixes the issue of non-conformance.

Answer 3

xCode 7.1 - ran into some issues but got it to work.

1. Imported through Cocoa Pods.

2. Bridging Header add:

   #import <MWPhotoBrowser/MWPhoto.h>

   #import <MWPhotoBrowser/MWPhotoBrowser.h>

3. Build Settings -> Header Search Paths add "Pods" set to recursive (fixes bridging header error)

4. Build Phases -> Link Binary with Libraries add: libMWPhotoBroswer, MediaPlayer.framework, libSDWebImage, libMBProgressHUD and libDACIrcularProgress (fixes 'symbol(s) not found for architecture x86_64' errors)

5. Build Settings -> Other Linker Flags add '-ObjC' (fixes errors with SDWebImage framework)

Hope that helps someone.

Answer 4

I got it working with swift 3.0, I has followed below steps:

(1) Edit MWPhotoBrowser.h file and find/replace " id <MWPhoto> " to " MWPhoto * "

(2) Implement required function as:

public func numberOfPhotos(in photoBrowser: MWPhotoBrowser!) -> UInt {
    return UInt(arrPhotos.count)
}

public func photoBrowser(_ photoBrowser: MWPhotoBrowser!, photoAt index: UInt) -> MWPhoto! {
    return arrPhotos[Int(index)] as MWPhoto
}