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While we’re on the subject of dealing with color choices, scroll down to the bottom and fill in the implementation for the chooseColor: method:

- (IBAction)chooseColor:(id)sender {

NSInteger selectedColorIndex = [(UISegmentedControl *)sender selectedSegmentIndex];

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults]; [prefs setInteger:selectedColorIndex forKey:@"selectedColorIndex"];

}

We’re nearly finished with this class, but we need to make one more change. Remember when we mentioned the autosaving that takes place when a document is notified that some editing has occurred, triggered by registering an undoable action? The save normally happens within about ten seconds after the edit occurs. Like the other saving and loading procedures we described earlier in this chapter, it happens in a background thread, so that normally the user won’t even notice. However, that works only as long as the document is still around.

With our current setup, there’s a risk that when the user hits the back button to go back to the master list, the document instance will be deallocated without any save operation occurring, and the user’s latest changes will be lost. To make sure this doesn’t happen, we need to add some code to the viewWillDisappear: method to close the document as soon as the user navigates away from the detail view. Closing a document causes it to be automatically saved, and again, the saving occurs on a background thread. In this particular case, we don’t need to do anything when the save is done, so we pass in nil instead of a block.

Make this change to viewWillDisappear::

- (void)viewWillDisappear:(BOOL)animated

{

[super viewWillDisappear:animated];

UIDocument *doc = self.detailItem; [doc closeWithCompletionHandler:nil];

}

And with that, this version of our first truly document-based app is ready to try out! Fire it up, and bask in the glory. You can create new documents, edit them, flip back to the list, and then select another document (or the same document), and it all just works. If you open the Xcode console while doing this, you’ll see some output each time a document is loaded or saved. Using the autosaving system, you don’t have direct control over just when saves occur (except for when closing a document), but it can be interesting to watch the logs just to get a feel for when they happen.

Adding iCloud Support

You now have a fully working document-based app, but we’re not going to stop here. We promised you iCloud support in this chapter, and it’s time to deliver!

Modifying TinyPix to work with iCloud is pretty straightforward. Considering all that’s happening behind the scenes, this requires a surprisingly small number of changes.

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We’ll need to make some revisions to the method that loads the list of available files and the method that specifies the URL for loading a new file, but that’s about it.

Apart from the code changes, we will also need to deal with some additional administrative details. Apple allows an app to save to iCloud only if it contains an embedded provisioning profile that is configured to allow iCloud usage. This means that to add the iCloud support to our app, you must have a paid iOS developer membership and have installed your developer certificate. It also works only with actual devices, not the simulator, so you’ll need to have at least one iOS device registered with iCloud to run the new iCloud-backed TinyPix. With two devices, you’ll have even more fun, as you can see how changes made on one device propagate to the other.

Creating a Provisioning Profile

First, you need to create an iCloud-enabled provisioning profile for TinyPix. Go to http://developer.apple.com and log in to your developer account. Then find your way to the iOS provisioning portal. Apple changes the layout of the developer areas now and then, so we’re not going into great detail about how the web site looks. Instead, we’ll just describe the basic steps you’ll need to take.

Go to the App IDs section, and create a new app ID based on the identifier you used when creating TinyPix. You can see this identifier by selecting the top-level TinyPix item in Xcode’s project navigator, selecting the Summary tab, and looking in the iOS Application Target section in the Identifier field. If you’ve been using com.apress as the base for your application identifiers, the identifier for TinyPix will be com.apress.TinyPix. You get the idea.

In the current version of the portal, we set the common name to TinyPix AppID, left the popup menu set to Use Team ID, and entered com.apress.TinyPix as the Bundle Identifier. Then we clicked Submit.

After creating your app ID, you’ll see it appear in a table showing various characteristics of each app ID. Under iCloud, you should see a yellow dot and the word Configurable. Click the Configure link next to that, and on the next page, click to enable the Enable for iCloud checkbox. Then click Done to go back to your list of app IDs.

Now, switch to the provisioning section and create a new provisioning profile specific to that app ID. The Provisioning section is just below the App IDs section. Click the New Profile button, and enter a Profile Name of TinyPixAppPP. If you don’t already have one, you’ll need to create a development certificate. In that case, click the Development Certificate link, and follow the instructions on that page. Once you have your development certificate set up, select TinyPix AppID as your App ID. Finally, select the devices on which you want your app to run.

When you’re ready, download the new provisioning profile to your Mac, and double-click it to install it in Xcode. In the TinyPix project window, select the top-level TinyPix object, select the TinyPix project itself (as opposed to the TinyPix build target), and then select the Build Settings tab. Scroll down to the Code Signing section, where you’ll find an item called Code Signing Identity. That contains an item called Debug, in which you’ll find an

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item labeled Any iOS SDK. Click the light-green popup in that row, and choose the developer certificate name listed under TinyPixAppPP.

NOTE: Dealing with certificates and provisioning profiles is a pain in the neck, but it seems to be a necessary evil in our little corner of the programming world. If it’s any consolation, as random as the current tool work flow seems, it’s actually a lot better than it was just a couple of years ago. If

this trend continues, perhaps in a few years, we’ll reach a point where configuring provisioning profiles will be as straightforward as creating a new project. We’re not holding our collective breath, but we’re keeping our fingers crossed. You might find it useful to work through the provisioning

specifics with a friend who’s been through the process before, and take copious notes!

The other bit of new configuration is, thankfully, quite a bit simpler. We need to enable iCloud entitlements for this project, so that it can make use of the iCloud capability baked into the provisioning profile.

Enabling iCloud Entitlements

With the top-level TinyPix item selected in the project navigator, select the TinyPix target from the list of projects and targets shown just to the right of the navigator. Switch to the Summary tab, and scroll down to the Entitlements section, which is currently empty.

Click the Enable Entitlements checkbox at the top of this section, and you’ll see that Xcode populates the remaining fields for you. It specifies an Entitlements File named TinyPix, and fills in your application identifier in the three other sections.

You’re finished! Your app now has the necessary permissions to access iCloud from your code. The rest is a simple matter of programming.

How to Query

Select BIDMasterViewController.m so we can start making changes for iCloud. The biggest change is going to be the way we look for available documents. In the first version of TinyPix, we used NSFileManager to see what’s available on the local file system. This time, we’re going to do things a little differently. Here, we will fire up a special sort of query to look for documents.

Start by adding a pair of properties: one to hold a pointer to an ongoing query and the other to hold the list of all the documents the query finds.

@interface BIDMasterViewController ()

@property (strong, nonatomic) NSArray *documentFilenames; @property (strong, nonatomic) BIDTinyPixDocument *chosenDocument;

@property (strong, nonatomic) NSMetadataQuery *query; @property (strong, nonatomic) NSMutableArray *documentURLs;

-(NSURL *)urlForFilename:(NSString *)filename;

-(void)reloadFiles;

@end

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@implementation BIDMasterViewController @synthesize documentFilenames; @synthesize chosenDocument;

@synthesize query; @synthesize documentURLs;

Now for the new file-listing method. Remove the entire reloadFiles method, and replace it with this:

- (void)reloadFiles {

NSFileManager *fileManager = [NSFileManager defaultManager]; // passing nil is OK here, matches first entitlement

NSURL *cloudURL = [fileManager URLForUbiquityContainerIdentifier:nil]; NSLog(@"got cloudURL %@", cloudURL); // returns nil in simulator

self.query = [[NSMetadataQuery alloc] init];

query.predicate = [NSPredicate predicateWithFormat:@"%K like '*.tinypix'", NSMetadataItemFSNameKey];

query.searchScopes = [NSArray arrayWithObject: NSMetadataQueryUbiquitousDocumentsScope];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(updateUbiquitousDocuments:) name:NSMetadataQueryDidFinishGatheringNotification object:nil];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(updateUbiquitousDocuments:) name:NSMetadataQueryDidUpdateNotification object:nil];

[query startQuery];

}

There are some new things here that are definitely worth mentioning. The first is seen in this line:

NSURL *cloudURL = [fileManager URLForUbiquityContainerIdentifier:nil];

That’s a mouthful, for sure. Ubiquity? What are we talking about here? When it comes to iCloud, a lot of Apple’s terminology for identifying resources in iCloud storage includes words like “ubiquity” and “ubiquitous,” to indicate that something is omnipresent— accessible from any device using the same iCloud login credentials.

In this case, we’re asking the file manager to give us a base URL that will let us access the iCloud directory associated with a particular container identifier. A container identifier is normally a string containing your company’s unique bundle seed ID and the application identifier, and is used to pick one of the iCloud entitlements contained within your app. Passing nil here is a shortcut that just means “give me the first one in the list.” Since our app contains only one item in that list (created in the previous section), that shortcut suits our needs perfectly.

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