Tag Archive for iOS

Crisis Coding: Stop The High-Res Madness

As someone who lives less than five miles from the Atlantic ocean in NJ, I’ve been having a bit of a bad time recently due to  Hurricane Sandy. Luckily, I was not harmed nor were any of my loved ones in the crisis. I did, however, notice something important: even  my non-techie friends and relatives were glued to their smart phones, hoping to hear some news about the storm, find out when their vital services (power / gas) might be restored, or (most importantly) check on their loved ones.

There are plenty of mobile apps that can be very helpful for handling a crisis, however, this recent crisis has shown me that there is something rotten in the state of app development — especially on the iOS side.

Let’s frame the scene a bit. During Sandy battery power was worth more than gold-plated platinum; for those of you unfamiliar with mobile development one of the most battery intense things most apps do is download data — especially image data. Up until today, I was out of power and the only access my fiance and I had to the outside world was out smartphones. Between us we have an iPhone 4S, a Galaxy Nexus, and a Lumia 900. We used all three phones to find pertinent data regarding the crisis.

I noticed some trends for roughly equivalent apps on each platform. The Windows Phone apps tended to load the fastest with the Android apps loading about as fast — I had no tools to do any real benchmarking, so these observations are all anecdotal. Sadly, my iPhone did not perform so well. I wondered why for a few minutes. After all, they were all on  3G  (the LTE Nexus had LTE turned off to conserve power) and the Lumia which was on AT&T should have been at a distinct disadvantage since Sandy had already claimed one of the local AT&T towers.

The difference was not with the network or OS’s or devices. It was about priorities in the apps themselves. While the Android and Windows Phone apps focussed on providing pertinent data in simple text based lists, the iOS apps were constantly trying to download images alongside the data. These images took a long time to load and therefore used an unnecessary amount of battery power. Worse still, after I regained my power earlier today, I reopened the iOS apps in question and they committed what is in my mind a mortal sin of mobile development: they all tried to download ‘retina’ resolution images over 3G.

Ridiculous. I understand that high-res images can make an app look good, but there is no need to download them over the air. Still, if you insist on downloading images that large, then please only do so over wifi. This is especially true if you app is geared toward helping people in a crisis.

A Look at PFQuery

Querying data is a pretty common task for most if not all mobile apps. iOS and Android have made the work pretty easier for developers, but Parse has thrown their hat into the ring to make it even easier for developers who choose to use their development tools and backend system; yes, I know this sounds a little like a commercial, but I am genuinely excited about this functionality and no I have no business or personal relationships with Parse or anyone therein.

PFQuery is a simple class that, as its name suggests, allows you to query your Parse dataset and getting data returned based on certain criteria. No need to stand on ceremony, let’s take a look at some code:

- (void) someMagicalFunction {
	PFQuery* query = [PFQuery queryWithClassName:@"SomeClass"];
	[query whereKey:@"SomeProperty" equalTo:@"MagicString"];
	[query findObjectsInBackgroundWithBlock:^(NSArray* objects, NSError* error) {
		// do something with the objects

	}];
}

And now for you Android fans:

void someMagicalFunction() {
	ParseQuery query = new ParseQuery("SomeClass");
	query.whereEqualTo("SomeProperty", "MagicString"
	query.findInBackground(new FindCallback() {
		public void done(List< ParseObject >objects, ParseException e) {
		// do something with objects
	});
}

Yup, that’s it. It really is that simple. If you want to know more take a look at the Parse docs. For those of you that are critical of Parse, I will be doing more than just code samples with it; in fact I have found a few deficiencies that I will be discussing in a future blog post.

WWDC 2012 Keynote Let Down

Earlier today I hosted Coder Radio with Chris Fisher of Jupiter Broadcasting and in the episode we discussed my reactions as a developer to the WWDC keynote this year (2012). First things first. I did not attend WWDC nor have I installed the iOS 6.0 developer release, so some of my information may be incomplete; I have to do this in this way due to Apple’s developer NDA. You can listen to the show to hear what I didn’t like, but I’d rather go through a few things that I would like to have seen that to my knowledge aren’t coming.

Inter-app Communications
This is by far my largest pet peeve with iOS development and using iOS. Why isn’t there are robust way for apps to work together and share data; within reason of course. Android has a version this in the form of “intents” and Windows Phone 7 has a incredibly powerful system called “contracts”. This really gets to me when I consider that iOS is a BSD system yet does not adhere to the UNIX philosophy of allowing many small applications to work together to do big things; yes, I know that iOS apps tend to be smaller in scope than their desktop counterparts but to date there is no real way for them to work together. There is so much functionality that cannot easily be done on iOS due to this restriction.

Widgets
On my Android and Windows phone I can glance at the screen and get the latest tweets, view other data (such as a stock ticker), and play a song, or begin or pause listening to an audiobook. On iOS, almost all of those things require me to launch separate apps. That’s silly not to mention a bad user experience. I know there are definitely battery life concerns if you have too many widgets open, but there is no reason that Apple can’t add some sort of restricted mode for simple widgets to run in.

Siri integration
Ever since I got my hands on my 4S I have been waiting for a full Siri API. Apple has been working on it, but to date there is no fully functional Siri API for third party developers. This is understandable given how often Siri simply does not work but it is still a shame.

That’s all for now. Now I can finally take a look at the dev preview! For feedback please find me on Google+ or Twitter.

Programming Pitfalls: NSAutorelease Pools on iOS 4.X

iOS 5 has brought a lot of quality of life improvements in terms of memory management and the general iOS development workflow, assuming you are on the latest tooling. However, nothing is free and there seems to be a little bit of a pitfall that you might hit if you are testing predominantly on iOS 5.x: iOS 5 seems to deal with autorelease pools a bit differently than 4.

Here’s the situation:

- (void) viewDidLoad {
  [super viewDidLoad];
  [self performSelectorOnMainThread:@selector(yourMagicalMethod) withObject:nil     waitUntilDone:NO];
}

- (void) yourMagicalMethod {
  // do some magical stuff and set some objects to autorelease
}

This will run fine and without complaint on iOS 5. However, on iOS 4 it throws some errors in the log at runtime regarding no autorelease pool being set and leaks every object you set to autorelease in yourMagicalMethod. If that isn’t enough to crash your app, then your app will be in a highly unstable state and will be prone to crashing the next time you do something even somewhat intensive, such as call the camera.

I did some sleuthing with Instruments and found that yes on 4.x those objects are all leaked and yes they are not on 5. Luckily there is an easy solution that doesn’t involve any crazy version checks or (God forbid) compiler macros:

- (void) yourMagicalMethod {
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

// do some magical stuff and set some objects to autorelease

  [pool release];
}

That’s it. All you need to do is create an autorelease pool in scope and release it. Both iOS 4 and 5 will be happy. I don’t know why this issues exists and I’d love to find out if you do. If you have questions or comments, I am on Twitter and Google+.

Phonegap the Bad and the Ugly

Times are tough and development budgets seem to be getting smaller and smaller, assuming that you are not Draw Something or Instagram. My experience has been that clients who are interested in supporting both Android and iOS do not generally want to develop two native applications. The reasons are obvious: cost and time.  So the conversation tends to turn to cross platform solutions. Currently, there are two types of cross platform mobile solutions for non-games: web based ones and Mono. I am currently doing a little work in Mono for Android and will write about that at a later date.

The most obvious web based solution is probably Phonegap. Phonegap has been around for a while and allows developers who have HTML/CSS/JS skills to leverage those to develop rich cross platform mobile apps. That’s all true. However, there are a few issues with Phonegap: it is not a mature platform, is a huge dependency, and is nowhere near as performant as native code.

This will probably be the most inflammatory issue I have with Phonegap, but I stand by it. Phonegap is not mature and it shows. A lot of the more complex and useful functionality comes from community plugins. However, the platform has to date been in such a state of flux, that you are likely to find that many plugins don’t work or at least don’t work without some form of modification on the most recent version of the platform. This may seem like a relatively small issue but if you look at it in terms of developer efficiency, then it becomes a bit more serious; do you want to be hunting down the right version of the right plugin for your version of Phonegap?

Dependencies are a necessary evil on any project and plugins are dependencies. Even if you are developing a native app you are taking a dependency on at least a language and one or more frameworks. Using a tool like Phonegap adds a big dependency on Phonegap itself which also depends on those native dependencies you were trying to avoid. Worse still, since the Phonegap must interact with Cocoa Touch or Android, there is a chance that you will have “mystery meat crashes” on one or both platforms. One example on iOS is that Phonegap does not do a great job with memory management, so your choices are use ARC (only recently an option), dropdown to Objective-C and write some “release” statements, or run the risk of seemingly random crashes in the wild.  Another issue with such a large dependency that depends on one or more distinct dependencies is that you end up with the lowest common denominator between all platforms. For example, there is no iCloud support in Phonegap nor is there Newsstand support. Someone could write a plugin for these but those would be yet another dependency in your app and any changes to Phonegap or worse Newstand or iCloud could break your plugin.

It is unlikely that you will be developing the next Infinity Blade, but performance still matters even outside of the games space. Phonegap is not as fast as a native app. It can’t be. Normally, this isn’t a huge issue for most apps but it is important to consider during the planning stages of your app especially if you want to use the camera or have a flashier UI; the camera is noticeably slower in Phonegap. As always, your app’s tolerance for the performance hit will depend a lot on the spec, but it is something to keep in mind.

Having said all that, there are cases in which Phonegap is a good choice. If budget is a huge issue, cross platform is a must on day one, the app will be pretty plain, and performance is not a chief requirement. As always, you need to pick the right tool for the right job, but remember there are no silver bullets. Questions? Comments? Rage? Find me on Twitter or Google+.

Simply Loading TableViewCells from a Nib

UITableViews drive a significant portion of iOS apps. Apple has provided some pretty great tools for developing decent looking apps based on them, but there are times when you might want to do something a little more stylish than what iOS provides. That’s when you probably consider writing your own UITableViewCell subclass or at least adding a category to UITableViewCell, though I find that is probably the less appropriate option in most cases. Getting your cells to look just right can be more than a little time consuming. Luckily, there is a bit of a shortcut you can take: loading the cells from a nib.

Before I show you how to do this, you should know going in that there are some drawbacks to doing this and that this is not an appropriate solution a some cases. Loading cells from a nib is less performant than just drawing the entire thing in code. Generally, you would not want to do something like this in a resource intensive app, such  as a game for example.  Ok, now that we have gotten that disclaimer out of the way, let’s get back to the point:

- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
   self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
   if (self) {
       NSArray* nibContents = [[NSBundle mainBundle] loadNibNamed:@"SpecialCell" owner:self options:NULL];
       NSEnumerator* nibEnumerator = [nibContents objectEnumerator];
       NSObject* nibObject = nil;
       while ((nibObject = [nibEnumerator nextObject]) != nil) {
           if ([nibObject isKindOfClass:[SpecialCell class]]) {
               self = (SpecialCell *)nibObject;
               break;
           }
       }
   }
   return self;
}

The above code presupposes that SpecialCell is a subclass of UITableViewCell; I omitted the header for the sake of brevity. So, let’s get the obvious stuff out of the way. This method is overwriting initWithStyle and yes you could write a second method rather than overwriting that one. We have the normal if (self) check that we see in inits. All pretty much standard.

Ok, so what is actually loading the nib? Well, if you look nib is being loaded and its contents are being placed in the nibContents array. Once the the contents of the nib are all in the array, an enumerator is created based on it. After that we simply loop through all of the objects, assign self the the one whose class is SpecialCell and return it.
Pretty easy, right? Just keep in mind that this can be a source of slow down on your table and may not be an appropriate solution for your app, but this can be a good time saver for prototypes or non resource intensive apps. If you have any feedback I can found Twitter or Google+.

All About ARC

ARC (short for automatic reference counting) is one of the most talked about and interesting additions to the iOS developer toolchain. However, in recent conversations with other developers I’ve found that there are a lot of misconceptions surrounding the technology. Hopefully, this clears up some of the confusion.

The first mistake that people often make when talking about ARC is that they equate it to garbage collection in languages such as C# and Java. This is simply incorrect. Boiling it down to its most basic explanation, a garbage collector runs in your application and checks to see what objects are no longer needed and removes them. This means that garbage collectors are very convenient for developers, but they take a small (depending on the implementation) amount of resources themselves. ARC is a special setting that can be set from within XCode that tells the compiler to insert release statements for you. So, this means that when you have ARC enabled the compiler is following the same retain / release rules you would normally follow for your own memory management, but this only happens at compile time, so there is no performance hit and you never see that statements themselves. This is useful because the compiler is far less likely to make a mistake than the average developer, especially in tricky situations, such as those that arise with multiple autorelease pools.

The second common belief developers hold surrounding ARC is that all their projects should use it. For new projects, this makes sense as long as you don’t mind targeting iOS 4.3+. However, converting legacy projects to use ARC can be a little hairy and like all magic that is made for developer convenience, when ARC causes a problem, it tends to be a tough one. Of course, that is not always the case and you mileage will certainly vary, but this is something to consider before hitting that shiny convert button.

Lastly, a number of developers that I have spoken to are under the mistaken impressions that all libs or external projects that you project is taking advantage of must be compatible with ARC for your codebase to use ARC. This is not the case. You can toggle ARC on and off for individual projects within your project (I know that sounds weird to me too) and safely use your legacy C libs or non-ARC Objective-C frameworks.

Overall, ARC is a great addition to the iOS developer’s toolbox, but it is like any other new technology and should be understood for what it is and adopted when appropriate.