Your application can create any number of NSOperationQueue objects, but the documentation suggests there is a practical limit to how many operations are executing at any given time. Specifically, adding additional queues does not mean you can execute additional operations. I find that a single queue is usually sufficient. Having access to a global operation queue means you can add, suspend, and cancel operations as needed. Add something like this to ApplicationDidFinishLaunching:

// Create the shared operation queue

sharedOperationQueue = [[NSOperationQueuealloc] init];

Notice all we did was change the selSucceeded selector to connectionSucceededWrapper:. The new wrapper method creates and adds the operation to the queue, as follows:

This post is part of iDevBlogADay, a group of indie iOS development blogs featuring two new posts per day. You can keep up with iDevBlogADay through the web site,RSS feed, or Twitter.

When using NSURLConnection there are only a couple of things to deal with. Unless you are using the synchronous version (not recommended) you will typically set up an object, such as your application delegate or a view controller, as a delegate to receive the NSURLConnectionDelegate callbacks. The main delegate message you need to handle are connection:didFailWithError:, connection:didReceiveData:, and connectionDidFinishLoading:.

One potential issue you face here is using a single object as delegate for multiple connections. Then your delegate message handlers will become messy as they attempt to determine which response goes with which request, etc. Now instead consider creating a utility class with just two public methods, like this:

myConnectionController interface

@interface myConnectionController : NSObject {
    NSMutableData* receivedData;
}
@property (nonatomic, retain) id connectionDelegate;
@property (nonatomic) SEL succeededAction;
@property (nonatomic) SEL failedAction;
- (id)initWithDelegate:(id)delegate selSucceeded:(SEL)succeeded selFailed:(SEL)failed;
- (BOOL)startRequestForURL:(NSURL*)url;
@end

Calling code example usage

id delegate = self;
myConnectionController* connectionController = [[[myConnectionController alloc] initWithDelegate:delegate
                                                                                   selSucceeded:@selector(connectionSucceeded:)
                                                                                      selFailed:@selector(connectionFailed:)] autorelease];
[myConnectionController startRequestForURL:[NSURL URLWithString:@"http://request.org/somequery.php"]];

Callback methods

- (void)connectionSucceeded:(NSMutableData*)data {
    // data contains response, e.g. JSON to be parsed
}
- (void)connectionFailed:(NSError*)error {
    // error contains reason for failure
}

myConnectionController implementation

@implementation myConnectionController
@synthesize connectionDelegate;
@synthesize succeededAction;
@synthesize failedAction;
- (id)initWithDelegate:(id)delegate selSucceeded:(SEL)succeeded selFailed:(SEL)failed {
    if ((self = [super init])) {
        self.connectionDelegate = delegate;
        self.succeededAction = succeeded;
        self.failedAction = failed;
    }
    return self;
}
-(void)dealloc {
    [connectionDelegate release];
    [super dealloc];
}
- (BOOL)startRequestForURL:(NSURL*)url {
    NSMutableURLRequest* urlRequest = [NSMutableURLRequest requestWithURL:url];
    // cache & policy stuff here
    [[NSURLCache sharedURLCache] removeAllCachedResponses];
    [urlRequest setHTTPMethod:@"POST"];
    [urlRequest setHTTPShouldHandleCookies:YES];
    NSURLConnection* connectionResponse = [[[NSURLConnection alloc] initWithRequest:urlRequest delegate:self] autorelease];
    if (!connectionResponse)
    {
        // handle error
    return NO;
    } else {
        receivedData = [[NSMutableData data] retain];
    }
    return YES;
}

And finally, the standard delegate methods for NSURLConnection are hidden inside the myConnectionController implementation. These should be familiar if you’ve ever used NSURLConnection directly:

NSURLConnectionDelegate methods

- (void)connection:(NSURLConnection*)connection didReceiveResponse:(NSURLResponse*)response {
    [receivedData setLength:0];
}
- (void)connection:(NSURLConnection*)connection didReceiveData:(NSData*)data {
    [receivedData appendData:data];
}
- (void)connection:(NSURLConnection*)connection didFailWithError:(NSError*)error {
    [connectionDelegate performSelector:failedAction withObject:error];
    [receivedData release];
}
- (void)connectionDidFinishLoading:(NSURLConnection*)connection {
    [connectionDelegate performSelector:succeededAction withObject:receivedData];
    [receivedData release];
}
@end

This post is part of iDevBlogADay, a group of indie iOS development blogs featuring two new posts per day. You can keep up with iDevBlogADay through the web site,RSS feed, or Twitter.

When the App Store opened, I dreamed of working for myself. After 26 years of service in academia and Corporate America I was tiring of enormous org charts and meaningless schedules. It took a little bit of time, but in late 2009 I finally quit my last day job. By then we had built up a little stable of apps, and the income was starting to pick up. I’ll never regret that decision, as many indie developers will tell you: once you work for yourself you’ll never want to go back to working for ‘the man’.

Year three on the App Store was an exciting one for us. Mundue apps have now been downloaded a total of 9.2 million times, about 95% of which are free apps. We released two new iOS apps this past year, and are working on a few more at the moment, and also created Mac and Android versions of reMovem. I gave a talk on ad network mediation at the Austin 360iDev conference, and met many new friends there and at other conferences. If you have the opportunity to attend the next 360iDev, this September in Denver, I highly recommend that you do so.

So what will year four be like? I’m very optimistic about the upcoming changes in iOS 5. With the sales of iOS devices still very strong, it looks like the next year or two will be even better for app developers. With over 400,000 apps in the store, the bad news is that your piece of the pie is constantly shrinking, but the good news is that the pie keeps growing ever larger with no slowdown in sight.

This post is part of iDevBlogADay, a group of indie iOS development blogs featuring two new posts per day. You can keep up with iDevBlogADay through the web site,RSS feed, or Twitter.

The changes in Lion are impressive; I consider it the most significant update since OS X was first released 10 years ago. Developers will want to rev their desktop apps to take advantage of the many new features, like Autosave, Resume, Versions, and Fullscreen. Some of the features we’ve long had on iOS are coming to the desktop in a big way, and this really does fulfill the “Back to the Mac” promise. If you don’t have a trackpad yet, you’ll want one for Lion. Lion’s on the immediate horizon with a scheduled July release.

Similar in scope is the iOS 5 update. Even if you don’t appreciate each of the 200 listed new features, you are going to be impressed with the new Notification Center, Reminders, and, hold the applause, wireless syncing. Billed as PC Free, Apple doesn’t even call this syncing, but it’s supposed to allow for wireless activation, backup, and updating. Although they’ve had some of this functionality on Android for a while, Apple’s superior user experience really shines here.

The game-changer of the three is of course iCloud, long speculated as Apple’s sync service “in the cloud.” But it’s much much more than that. By seamlessly storing data in a central wireless repository and automatically syncing it to all your devices (desktop & mobile), the problem of syncing multiple devices should be eliminated. Like many, I’ve suffered though the pain of MobileMe duplicating and removing contacts, calendar entries, and email settings. With six iOS devices and three Macs sitting in front of me right now, this solution can’t come soon enough. I expect some new breeds of apps designed to take collaboration (with self & others) to the next level. In addition, even for casual games like reMovem it will be easy to save game state so you can start it on your iPod touch and finish the same game later on your iPad.

If iCloud is the glue that holds apps together, then Xcode 4 is the all-in-one tool needed to build them. In order to work with any of the newer SDKs you should already be using a version of Xcode 4. I hesitated for quite some time, mostly because my experience with the early pre-release versions was less than satisfactory. Around the time of the VTM Seattle conference (early April) I made a conscious effort to switch from Xcode 3.2.6 to Xcode 4. Honestly I haven’t regretted it one bit. I know there are some things that don’t work right, but luckily I’m not using the Core Data modeling which is broken. If you do, then I can understand the hesitation.

I’ve been using Xcode 4 exclusively now for 3 months and it’s really a nice improvement in many ways over the previous versions. I’ve used it for a couple of client projects and submitted three of my own apps with it during that time. Once you get over the learning curve, and it is steep, you’ll be happy you made the switch. We’re often asked by new developers, “Where do I start?” Although all of the beginning iPhone development books reference Xcode 3, you’d be better suited to dive into Xcode 4 right away and avoid any uncomfortable transition.

After seeing some of the presentations at WWDC when the Apple folks made Xcode do the almost-unthinkable, it’s clear that its capabilities (now, and planned for the near future) were carefully thought out. Yes it’s a beast, but one you can customize to fit your workflow if that’s your preference. If you’re still on the fence about Xcode 4, I recommend you give it a try soon so you can get on with the new shiny bits. Lion is nearly upon us, and iOS 5 awaits your exploration!

This post is part of iDevBlogADay, a group of indie iOS development blogs featuring two new posts per day. You can keep up with iDevBlogADay through the web site,RSS feed, or Twitter.

Yes the conference has grown a great deal since the 1990′s in San Jose. I think there were barely 1,000 attendees that year. But it’s still easy to find people in the crowds or in the streets around the conference center. Most will have iPhones or iPads and Twitter at the ready, and the proliferation of third-party events means you’ll likely run into someone more than once without even trying.

There are an awful lot of To Be Announced sessions at the time I am writing this. I’m not sure what to make of it except that we’re sure to see a few surprises this morning. No, we won’t be getting free iPhones, but around noontime today I guarantee we’ll all be maneuvering to plug in ethernet cables and download the pre-release of [REDACTED].

If you’re not here I’m sure you’re watching a live stream of the day’s events. Hang in there, all will soon be revealed. If you are here and you see me, please say hi!

This post is part of iDevBlogADay, a group of indie iOS development blogs featuring two new posts per day. You can keep up with iDevBlogADay through the web site, RSS feed, or Twitter.

The Symptom

I was in the middle of updating a project with the latest AdWhirl and Millennial Media SDKs. If you are not familiar, the AdWhirl SDK uses the Millennial Media SDK and both have been changed recently to use a newer method in the MMAdView class. This ended up causing a runtime error, followed by a helpful stacktrace:

2011-05-10 17:11:43.105 reMovemFree[1630:707] +[MMAdView adWithFrame:type:apid:delegate:loadAd:startTimer:]: unrecognized selector sent to class 0x118c48

2011-05-10 17:11:43.184 reMovemFree[1630:707] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+[MMAdView adWithFrame:type:apid:delegate:loadAd:startTimer:]: unrecognized selector sent to class 0x118c48'

I puzzled over this for a few hours trying to figure out just why this happened. The headers files were correct, and obviously the project was linking without a problem. At this point I didn’t want to write any more debugging or introspection code, but I was really just looking for a way to find out exactly which methods the class did support. That turned out to be a dead-end anyway.†

The Cause

If you work with 3rd-party SDKs you might be accustomed to taking updates every few months or so. After some time you have probably updated certain libraries many times. I know I do this quite often. Many of you are probably way ahead of me here and can see where this is going. When you (literally) drop in a new SDK, and delete the old one, Xcode adds the new SDK path to the Library Search Paths for the project. Which is fine:

The problem is that Xcode didn’t delete the old SDK from the search paths when I dragged it out of the project. Since the build links with the first version of a library it finds on the search paths, any older version will usually do. Here’s what happens after repeatedly dropping in new versions of SDKs:

So what really happened was that I was linking to the earlier version 4.1.0 of the Millennial Media SDK, not the latest 4.2.4, even though both were on the library search path. This seems like a deficiency in Xcode, since it appears to go to lengths to track external referenced file dependencies.

The Solution

The simple solution for me was to go in and manually prune the old SDK paths from the Library Search Path setting for my project. And of course, add a note in my “todo” list for future updates to take care when adding new SDKs. Unfortunately the Xcode 4 widget for editing the Library Search Path setting is a little funky compared to the Xcode 3 version. I managed to get it shrunk down so small it is barely usable, but with a great deal of patience I was able to find and zap the offending entries.

Incidentally, you may want to take advantage of Xcode’s Source Trees preference, which lets you define an external folder, give it a symbolic name, and refer to in inside your project. This is super handy for two reasons, 1) it dramatically shortens all the nearly-unreadable $(SDKROOT)/../../../etc paths, and 2) it makes code portability to different machines with different folder structures much easier. It turns this:

into this:

Hope this helps a little, even if just to remind you to double-check those Library Search Path settings next time you drop in a new replacement library from a 3rd-party vendor. If you know of a better way to manage this issue, I’d love to hear about it.

† The commandline tool “otool” is great for examining dynamic and static libraries. The problem for me was that I examined the libraries I assumed were linking, not the ones that were actually linking. Looking at the wrong library didn’t help, since it obviously had the right method signatures:

This post is part of iDevBlogADay, a group of indie iOS development blogs featuring two new posts per day. You can keep up with iDevBlogADay through the web site, RSS feed, or Twitter.

I rolled my own code to prompt users for a review and the results have been excellent. We’re now getting mostly 4 and 5 star ratings in the prompt-enabled apps. The key of course is in the timing of the prompts. I’ll explain a little about how the code works, then discuss the results so far. For a far better complete code template and explanation see also Noel Llopis’s blog post from last year.

Since the stated objective is to get positive feedback without annoying the user, we want to filter out people who have just launched the app for the first time. One way to do this would be to use a timer, maybe wait until some period of time has elapsed. That’s probably OK, but could lead to a prompt coming up at a truly random time. Instead I have code that checks for two things: time elapsed plus a new high score achieved. To detect a desired length of time, use something like this in your -[UIApplicationDelegate application:didFinishLaunchingWithOptions:] method:

if (![defaults objectForKey:kFirstRunKey]) {

    [defaults setObject:[NSDate date] forKey:kFirstRunKey];

}

This gives you the timestamp of the first run time. I typically define kFirstRunKey to include a unique version number, so I can record the first run of each update. Now each time a new high score (use whatever criteria you see fit) is achieved, check the current time against the first run timestamp, like this:

- (void) askToRateApp {

 if ( ![self reachable] )

   return;

 NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];

 if ( [defaults boolForKey:kAlreadyDeclinedToRateKey] )

   return;

 NSTimeInterval elapsed = [[NSDate date] timeIntervalSinceDate:[defaults objectForKey:kFirstRunKey]];

 if (elapsed < kAskDelaySeconds ) // approximately 1 day

   return;

Notice a couple of interesting things here. First, I have a Reachability test to exit early if there’s no connection. Second, if the user has previously declined to rate the app, respect that choice and do nothing. Finally, there is a test to see if enough time has elapsed. If not, again do nothing. At this point you could prompt the user, or optionally add more tests. Maybe you only want to prompt on the 17th high score. Then something like this would work:

 NSInteger showAsk = [defaults integerForKey:kShowAskToRateKey];

 // If showAsk is 0, the prompt screen will be shown.

 // If showAsk is > 0, we decrement it now.

 if ( showAsk == 0 ) {

   feedbackAlert = [[[UIAlertView alloc] initWithTitle:NSLocalizedString(@"AskToRateApp",@"") message:nil delegate:self cancelButtonTitle:NSLocalizedString(@"NoThanks",@"") otherButtonTitles:NSLocalizedString(@"RateNow",@""), NSLocalizedString(@"RemindLater",@""), nil] autorelease];

   [feedbackAlert show];

 } else {

   showAsk = (showAsk - 1) ;

   [defaults setInteger:showAsk forKey:kShowAskToRateKey];

 }

}

In this example, the showAsk variable is tested to see if the counter is zero. If it is, we show the feedback alert. Otherwise we decrement it and store it back in the default settings for next time. Set a reasonable initial value for kShowAskToRateKey. Once the saved value reaches zero, the alert will be shown exactly once. All that’s left to do is handle the buttons on the feedback alert.

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex

{

  if ( alertView == feedbackAlert ) {

    NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];

    if ( buttonIndex == 0 ) {

      // No Thanks

      // Don't Ask Anymore

      [defaults setBool:YES forKey:kAlreadyDeclinedToRateKey];

    } else if ( buttonIndex == 1 ){

      // Rate Now...

      // and Don't Ask Anymore

      [defaults setBool:YES forKey:kAlreadyDeclinedToRateKey];

      [self showAppStoreReviewPage];

    } else if ( buttonIndex == 2 ) {

      // Remind Me Later

      [defaults setInteger:21 forKey:kShowAskToRateKey];

    }

    feedbackAlert = nil;

  }

}

For the “remind later” choice here, I’m resetting the kShowAskToRateKey to 21, but this can be any value you like. I recommend you use analytics or some other method to determine an appropriate measure of how much time is “later.” FInally you need a small piece of code to make the App Store review page show. This technique can be used on iPhone, iPod touch, iPad, and Mac, but on iPad and Mac it is not possible to go directly to the review page. You’ll go instead to the App description and may want to explain how to actually enter a rating or review in those cases.

- (void) showAppStoreReviewPage {

  [[UIApplication sharedApplication] openURL:[NSURL URLWithString:deepLinkReview]];

}

For the deepLinkReview you will specify the URL that takes users to the application’s review page on iTunes. It’s pretty straightforward to construct the URL manually. Justine Pratt wrote all about this on her blog last year. You can also wrap the URL in a LinkShare link if you are an iTunes affiliate.

So how well does it work? Like Noel I have see an improvement in reMovem ratings from 3.5 stars to 4.5 stars, with about twice as many written reviews per day as there were a year ago. Still, 2 out of 3 users choose not to leave reviews. Of the rest, half opt for the “remind later” choice while about 15% click the “rate now” button. I suspect only a percentage of those actually complete the process, but it’s better than none. It’s debatable whether this leads to more sales, but having more 4 and 5 star reviews certainly helps when people are looking at the App Store description. I also believe they use the number of reviews as a gauge to an app’s popularity, and, in turn, as a data point for their purchasing decision. So the more reviews, the better.

—-

This post is part of iDevBlogADay, a group of indie iOS development blogs featuring two new posts per day. You can keep up with iDevBlogADay through the web site, RSS feed, or Twitter.

Nevertheless, from the very beginning it was a pleasure to deal with the folks at Aptocore. The system they built was easy to integrate and manage, and the SDK had an excellent Xcode-integrated documentation set. The support team was knowledgeable and courteous, and always very professional. We’ll miss working  with them, and wish them well in their future endeavors.

Many developers used AGON in some interesting games. A few of my favorites were: Eyegore’s Eye Blast, Similis Deluxe, Sheepstacker, Popper, Inkvaders, SpringFling, and Azplode. Check ‘em out!

Soon we’ll be heading to Seattle for the biannual VTM iPhone conference. This two day event will be held the weekend April 9-10, with an optional third day of seminars the day before. This will be my third Voices That Matter conference, and I’m looking forward to some great sessions and seeing old friends again. I’m also very interested in the hands-on cocos2d seminar with Rod Strougo and Ray Wenderlich on Friday. For those new to Cocoa and Objective-C there’s also a full-day session with the Big Nerd Ranch guys Aaron Hillegass and Joe Conway.

Most of the presenters at VTM are authors and experts on iOS development, which leads to the motto of “learn from those who wrote the book.” There’s a fun vibe at VTM, although I wish it were longer than 2 days, and Seattle is great in April, so this is a great opportunity to meet and hang out with other iOS developers. Since we’re driving up from Colorado this also offers the opportunity of a road trip across a part of the US that we’ve never seen.

It’s not too late to register, and discounts are still available, so, hope to see you there!

Last weekend I had the privilege to be able to attend the inaugural 360MacDev conference in Denver. While many readers may only be beginning to think about deploying apps on OS X, there are many developers out there who’ve been happily making a living doing so for years. The overlap, or synergy, if you will, of the iOS and OS X communities was clearly evident at the conference.

Since this was the first 360MacDev it was small and everybody sat in on the same sessions. There was a great mix of in-depth technical talks, design talks, app store talks, and a few of Mike Lee‘s dirty jokes to kick things off. If you couldn’t attend be sure to look for the next one in 2011. We got to spend some time with old friends and make a few new ones, and it was nice to see the young crowd (12 year olds Charlie and Santiago) again in attendance. Hate to think what I was doing at that age. It’s hard to pick, but one of my favorite sessions was John Pannell‘s Get Connected! talk about the various network capabilities on OS X.

Yes, there was a lot of speculation and trepidation about the upcoming Mac App Store. Fact is, we don’t have many real answers yet, but in a few short months all will become clear. Michael Simmons covered what we know from previous experience on the iTunes App Store and existing Mac sales channels. According to Jay Freeman there will be a Cydia Mac Store for those that aren’t interested or able to get their Mac apps past the Apple approval process. It’s not hard to imagine that he’ll be just as successful in an environment where the devices have never been incarcerated in the first place.

Putting together such an event is slightly more complicated that renting hotel rooms and selling tickets. That’s where credit is due to John and Nicole Wilker, creators of the 360 Conferences empire. They’re able to consistently attract top speakers and keynoters, which makes attending a no-brainer for me. Sure, I live in Colorado, which means I didn’t have to fly to Denver. But I know it was well worth it, even for my friends that had to fly there. Because their focus is the community itself, these smaller 360 conferences are much more personal, and have no “corporate” feel.

That’s why it’s nice to see John get recognized as an influential young Coloradan. The work he and Nicole do is much appreciated by the Mac and iPhone developer community. John’s pretty low-key, he’d probably rather be sitting in attendance with the rest of us than running around attending to details. Glad they are up to the task. Job well done!

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