Author: igo

One of the most asked features of the Cheat-sheets app was to add the possibility to change the font size of the cheats/notes on the users’ Apple Watch. Yesterday this feature was added to the app.

So, how to add settings to the Apple Watch? In general there are two ways to proceed. One option is to add some custom “Settings” button in your iOS app and let user to configure Watch-settings. Maybe this is also the way I’ll go in the future. But for now I decided for the second option to utilize the standard way that Apple suggests, i.e. settings bundle.

How to add Settings-Watch.bundle to your app is best describe at the Apple’s docs. I also found useful this blog posting. Following steps are required:

1. Add Settings-Watch.bundle file to your iOS target. Yes, to your iOS app and not the WatchKit target 😉
2. Enable the App Groups capability for your iOS app, WatchKit extension, and Watch app
3. Important: add the ApplicationGroupContainerIdentifier key to the Root.plist file of your Settings-Watch bundle. Place the key somewhere at the top level of your property list. Set its value to the identifier you specified in the App Groups capability
4. Define your settings
5. To localize your settings bundle just duplicate lproj folders and call them like de.lproj or ru.lproj. Use Root.strings files for translations.

So now the settings must be visible in the Watch-App of your iPhone like this:

To access the settings in your Watch app, i.e. some WKInterfaceController just use the code:

let defaults = NSUserDefaults(suiteName: "group.com.example.MyWatchKitApp")
let enabled = defaults?.boolForKey("enabled_preference")

In the Cheat-sheets app the changes of the Settings are immediately seen in the Watch-App. Be aware that your Watch app will not be notified about changes in your NSUserDefaults, because they are changes in another process. That is why this will not work:

NSNotificationCenter.defaultCenter().addObserver(self, selector: "loadFontSize", name: NSUserDefaultsDidChangeNotification, object: nil)

You have to add KVO observer to every parameter in your NSUserDefaults:

let preferencesUserDefaults = UserDefaults(suiteName: "group.com.example.MyWatchKitApp")
                preferencesUserDefaults?.addObserver(self, forKeyPath: "enabled_preference", options: NSKeyValueObservingOptions.new, context: nil)

To listen to the changes just override the function:

    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        
     // do your stuff here
    }

And of course do not forget to unregister the observer if you do not need it anymore.

Using UIImagePickerController it is easy to take a picture in your iOS app. The picture is not immediately saved in the photo library. You must apply UIImageWriteToSavedPhotosAlbum method to write it there. In some situations you need to know the name of the file that the photo library assigns to the image. For example you have an option in your app also to select an image from the photo library. And you want to avoid that the user picks the same photo. So, how to know the name of the file that photo library assigns to the photo? There is a delegate method imagePickerController:didFinishPickingMediaWithInfo:. We make a use of it:

- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
{
    PHAsset *asset = nil;
    PHFetchOptions *fetchOptions = [[PHFetchOptions alloc] init];
    fetchOptions.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:YES]];
    PHFetchResult *fetchResult = [PHAsset fetchAssetsWithMediaType:PHAssetMediaTypeImage options:fetchOptions];
    if (fetchResult != nil && fetchResult.count > 0) {
        // we sorted the photos by creation date and get the last photo from Photos
        asset = [fetchResult lastObject];
    }
    
    if (asset) {
        // get photo info from this asset
        PHImageRequestOptions * imageRequestOptions = [[PHImageRequestOptions alloc] init];
        imageRequestOptions.synchronous = YES;
        [[PHImageManager defaultManager]
         requestImageDataForAsset:asset
         options:imageRequestOptions
         resultHandler:^(NSData *imageData, NSString *dataUTI,
                         UIImageOrientation orientation,
                         NSDictionary *info)
         {
             
             if ([info objectForKey:@"PHImageFileURLKey"]) {
                 // path looks like this -
                 // file:///var/mobile/Media/DCIM/###APPLE/IMG_####.JPG
                 NSURL *path = [info objectForKey:@"PHImageFileURLKey"];
                 if(path) {
                     NSString *filePath = [[LPPathUtilities applicationDocumentsFolderPath] stringByAppendingPathComponent:[path lastPathComponent]];
                     
                     NSData *dataFromImage = [NSData dataWithData:UIImageJPEGRepresentation(image, 10.0)];
                     if(![dataFromImage writeToFile:filePath atomically:YES]) {
                         // TODO: handle error
                     }
                 }
             }
         }];
    }
}

Unfortunately, the key PHImageFileURLKey is not specified in the Apple documentation. So, there is of course a danger, that this can key can change in the future. But I could not find so far a more easy approach how to get the file name. If you have a better idea, let me know 😉

In our large iOS project that was started 2008 and that will be 10 years old this year we use much XSL transformations. This technology was the first choice at that time to deal with structured data and its representation on mobile devices. Nowadays similar uses cases can be covered by JSON and Java Script. Probably this is the reason, why WKWebView the newer component that Apple recommends to use instead of UIWebView contains no support for XSLT.

The only way to support XSLT in your app is to integrate some third party XSLT library. We decided for libxslt. That’s a C library based on libxml2. Instead of loading XML file in the WKWebView (this was possible with UIWebView) we start XSL transformation first and generate html file. Generated file is then loaded with WKWebView.