auto reference counting with iOS 5.0

iOS 5.0 introduced us to ARC for mobile. this is a major change (advantage) in the way developers  work. what was once a source for memory leaks, which required diligent memory allocation and management, becomes easier and much simpler of a task, allowing developers to focus on the code.

LLVM rocks indeed.

think of it as new ‘best practices’ one should incorporate into their coding habits, while disallowing other practices:

  • no more retain, release, autorelease nor dealloc
  • no more custom retain nor release method implementations
  • do not store obj pointers in C structures (use objects instead)
  • no more direct casting between objects and non objects (e.g. id and void*)
  • you are done with NSAutoreleasePool. use @autoreleasepool keyword to mark the block in curlies.

what ARC should encourage you to do is start thinking about the relationship between objects and object graphs, and not so much in terms of retain/release. there is now a new lifetime qualifiers for objects, which includes zeroing weak references. the value is automatically set to nil when the object it points to is deallocated. we now have qualifiers for vars and new weak and  strong declared property attributes.

apple is providing developers with migration tools which are build into xcode:

https://developer.apple.com/library/ios/documentation/DeveloperTools/Conceptual/WhatsNewXcode/00-Introduction/Introduction.html#//apple_ref/doc/uid/TP40004626 .

switching to ARC means neglecting support for iOS >5.0.
add custom containers to the mix, much more control over customizing UIKit elements, storyboards, tableView’s new flexibility and much more.

happy coding.

iPad 3 predictions

the ipad3 is around the corner as apple just announced a media event on march 7th.

ipad3 event invitation what will we possibly get?

  • retina display: 2048×1536 pixels will make pretty much everything more gorgeous and engaging.
  • A6 quad core processor: this means tremendous performance and response boost.
  • LTE support. let’s face it – 4G network is where it’s all heading,
    as the internet will blend better and tighter with the device and our lifestyle.
  • better front and back camera. flash.
  • equal or better battery life.
  • unified GSM/CDMA support.
  • bluethooth 4.0 chip.


what we may get:

  • smart bezel virtual buttons:
    imagine the bezel and back cover of the ipad responding to customized buttons which lit up.
    so you can setup the top left .bezel button to launch maps. more here.
  • NFC chip (not likely IMHO).
  • airdrop feature from ipad to mac.


what we probably won’t get yet:

  • haptic feedback display. the game changer. it will be a great day when it arrives (though the image from apple may hint at it…).
  • solar charging of the device
  • new map system which apple has been working on

final thoughts:

  • how does siri fit in? i am not sure yet…
    will iOS 6.0 be announced as well? if so, developers will a beta by early next week…

from: iphone -> ipad; a quick guide.

it’s time to expand your iphone app and introduce it on the ipad. that is an interesting move for any product as the ipad is not an iphone – it is used for different things at different circumstances. yeah – you are going to practically re-think your app… which is great because you get to revisit your code and make sure your pipeline is tight, secure, fast and reliable. all that with the elegance of the ipads – split view controllers

where do one starts? well, you can start be designing your app for the ipad and take by thinking about the following:
orientation, layout and gestures. all of which vary significantly from the iphone (unfortunately). side note: one thing i really like about webOS is that you develop your mobile app once and the system takes care of adjusting the interface to a slated device.

next thing to learn about the ipad is it’s split views, popovers and specific hardware features – all of which are ipad unique. you will need to use conditional coding to learn if a specific hardware feature you are looking for is available. this is necessary as you will need to load the right resources to handle that hardware. more specifically one should write conditional coding for:

resources: in your code, recognize which platform is running and load the right nib files. you will also need to load the right graphics that match the screen size and resolution.
classes: check for class availability based on the device you are running on as some are iPad/iPhone specific.
methods: weak-link any device specific methods and perform a check at runtime for the availability of that method and wether the object responds to a specific selector.

hardware: test for cmarea/gps/gyro support before utilizing it.

okay – we are done with the overview. let’s roll up our sleeves and dig right into it.

first thing’s first – lets let xcode help us start the process by duplicating the current target (an iphone target) into an ipad one.
right click on your target and choose “duplicate”. two options here – duplicate only and duplicate and transitoin to ipad. let’s go with the later.
what xcode does here is create a new virtual folder (i.e. group) called “Resources-iPad” and copies the main nib file there. xcode really takes care of the main nib file and creates it for us. no other nib files to be touched. why? because the rest of the nib files are usually tied right into apps view controller so xcode leaves it up to us to define both the view and it’s controller. xcode sets the targeted device family (TDF) build settings to iphone/ipad and modify the base SDK of the project which will support both device types. no need to touch nor worry about the deployment target. you will see a new plist for the ipad app with it’s relevant settings.

in order to see it in action – run the app using the ipad simulator. what you will see is the iphone app running inside the ipad simulator and you can x2 time it to fit. boooo. one more step necessary (thanks apple for leaving it up to us) is to update the scheme to use the new and shiny ipad target. so go ahead and duplicate your iphone scheme (or create a new one) and under run  – choose the ipad executable. boom. wait – it really looks bad here.

well – as you may know iOS uses the MVC design pattern heavily. you may not know that MVC is actually a compound design pattern which includes 5 patterns. luckily this abstraction makes the process of porting an iphone app to an ipad a bit easier, as potentially one needs to take care of the view – making sure the right outlets are updated based on the design of the UI, and also heavily touch upon the controller to see which device is used and then follow a specific code path to match. the good news is the model can stay untouched 🙂

if you are happy with the IBOutlet you currently have on the iphone and would like to only use those (i cannot image why, but yeah…) all you need to do at this point is adjust the springs and struts in the size inspector when loading up your nib in IB. you should also make sure to support the orientations required for the app. in order to do this you will need to  implement shouldAutorotateToInterfaceOrientation:  and test for the device running the code and allow rotation. if you have singleton object place this code in it’s header file:

#define IS_IPAD   (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad)
#define IS_IPHONE (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone)

ipod touch returns UIUserInterfaceIdiomPhone. FYI.

or place it wherever works for you, as long as you have access to this macro from wherever. this is useful as you will need to update your controllers to test for the hardware running and follow a specific code path to update your view and outlets.

one example of using this code and auto rotating is this:

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {

	 if (IS_IPHONE)
	 {
		 if (interfaceOrientation == UIInterfaceOrientationPortrait ||
			 interfaceOrientation == UIInterfaceOrientationPortraitUpsideDown)
		 {
			 return YES;
		 }
	 }

	 if (IS_IPAD)
	 {
		 if (interfaceOrientation == UIInterfaceOrientationLandscapeLeft ||
			 interfaceOrientation == UIInterfaceOrientationLandscapeRight)
		 {
			 return YES;
		 }
	 }

	 return NO;
 }

pretty easy and straight forward right? moving along.

cautionary tale:
the app now must be careful with the symbols it uses. if you want to use UISplitViewController while running on iOS 3.1 – your app will crash as there are no split VCs on 3.1.
the way you should be thinking about this is by mentally tuning into the ‘runtime checks’ zone, where you will test if a particular symbol exists. more about that later.

updating VC and views:
this is where the bulk of the work really is – redoing your views and adding code (or creating new) view controllers. what can we do – the view size varies between the iphone and the ipad and that certainly needs to be taken into consideration. so start off by redesigning the views for the ipad. if you plan on scaling the existing view could work okay, but more often than not will not be the result you are hoping for. think of it this way – the new ipad interface should make use of the new available space and the elements which only exist on the ipad (splitVCs and popovers for example). the outcome is good UI and top UX.

also consider the following. for view controllers:
a) create new nib files for each device (if you use nib files that is).
b) if you code your views – make sure you support both devices when you do so.

for views:
a) if you override drawrect: make sure the method can draw to different view sizes.
b) if you implemenet the layoutSubviews method, the code must adapt to different view sizes.

symbol checking during runtime:   if deep down inside you had hoped that this step will somehow be avoidable – fear not 🙂 runtime checks for newer symbols is easy as pie and is the type of topic you can discuss with your boss and sound really clever.
all of this is under the assumption you support different versions of the OS. just like a good soldier – you MUST protect your code from using symbols that do not exist. this happens all the time when you update an app to use new features and want to continue to support previous versions running on older OSs. all you need to do is create different code paths to follow, based on the OS currently running on the device executing your app. if you don’t do that your app is guaranteed to crash and that is not something us pros do, so let us quickly look into an example of how one goes about creating a code path when checking for newer symbols during runtime:

if you are linking against iOS 4.2 you are in luck my friend. that version has a weak linking support built right in, which allows you to check for the existence of a given class object and determine if it’s usable to you. like so:

if ([UIPrintInteractionController class]) {
   // Create an instance of the class and use it.
}
else {
   // The print interaction controller is not available.
}

seriously now – how simple was that?
bare in mind that if you want to use this feature of the OS you must build your app with LLVM and Clang.
deployment target should be 3.1 or later. sorry.

if your app links against < 4.1, use NSClassFromString to see if a class is defined. if nil is returned – you’re shit out of luck.

for example:

Class splitVCClass = NSClassFromString(@"UISplitViewController");
if (splitVCClass)
{
   UISplitViewController* mySplitViewController = [[splitVCClass alloc] init];
   // Configure the split view controller.
}

for testing if an object  can be sent a specific message (i.e. has implemented that method), use the oh so convenient instancesRespondsToSelector: class method (yes, it is a class method, it’s not a type).

if you are a registered iphone developer and have not done so – check out the SDK compatibility guide by apple.


runtime checks –> conditional code paths:
based on the interface idiom described earlier – let’s start creating cool code paths to support both devices. a simple if-else statement will do just fine thank you very much. moving right along.

This concludes this first steps required to port your app from iphone to an ipad. next is a quick rundown on how to use split view controllers in your ipad app.
 

iOS 5 is around the corner (updated)

iOS 5 image

update: this post was written thursday of last week. it is now semi confirmed the developer of mobileNotifier is hired by apple and that iCloud will be presented by jobs tomorrow.

one major revamp is the bare minimum as there are areas lacking where either android or cydia leaves the current OS lagging. and no doubt we will get what we are expecting.. just a gut feeling… here is my short list of enhancements that i’d like to see:

1. improved notification system: bar non that most important and required change to iOS. face it, the current notification system sucks big time. in the past, the real incentive to jailbreak your phone was mywi, my3g and going even further back, multitasking and naturally the most important feature – sim freeing your phone (Screw you apple and ATT for violating FCC regulations). now-a-days, mobileNotifier is THE reason why my phone is jailbroken. aggregate all notifications into a single window utilizing the empty space created when you double click the home page. apple – pls take note, this guy has done a great job.

2. dynamic home icons: ala windows8. yes you heard right. big chunky icons that actually display content and not just a static image. one good example is available on cydia and is called ‘weather icon’. it changes the degrees on the weather icon to display the current temperature. it also allows the temperature to be displayed on the status bar. really useful stuff. apple, please expose an API to do so.

3. OTA updates: not likely but definitely nice to have… over the air updates makes lots of sense. please – no more plugging in to itunes and backing it all up. this ties up to the next item that is most definitely making an appearance on monday:

4. iCloud content sync: this will probably make a big eco. iCloud can and will take cloud services to the next level. apple doing what they do tiered up, may see music sync and later down the road app sync.. so iCloud will probably allow you to purchase music from iTunes and stream it directly from your cloud storage. no need (or an option) to download and sync stuff. fantastic. one viable option is to open a US front against spotify, the EU-stream-the-song-you-want kind of service in the US. imagine a yearly/monthly plan ($20-$50/year) where you can listen to what you want… that’s a nice one.

WHAT’S MISSING? iphone5 with 4G, NFC and iWallet, A5, double down on RAM, larger display and IR.

useful xcode debugging methodologies

developing for the iponhe is not a simple thing. cocoa is designed with specific patterns in mind, a dominant model-view-controller, performance oriented with specific ways of going about things. xcode is your best friend, believe it or not. the apple documentation is there for you as well, and many hours were spent to create coherent manuals that will assist us in doing a great job. and doing a great job is a must, because mobile devices are not as browsers. memory foot print is really important. if you over due it, your app will be removed by the OS and UX breaks. bad karma indeed.

dealing with memory leaks and zombies is an important issue, and below i will provide a couple of useful tips to setting up xcode in such a way, and arranging your code, so you have more control and understanding of what’s going on under the hood.

first up, i assume you are familiar with:

– reading a call stack
– play around with the expression window
– use the memory browser when needed

if you are not, you probably should read up on those and play around with them. very useful tools to get the gist of what is going on with your app.

tip #1:
– always archive your dSYM (short for debug symbols) along with the app you send for your QA guys (the “testers”). this is really useful, as once they email you back crash logs (which they will), the data in the log will actually make sense, i.e. the symbols are mapped correctly and you will see actual method names rather than HEX addresses.

tip #2:
use the symbolicatecrash script and pass it the .crash file and .dSYM file. this will allow you to mesh the two together and review what had happened. from the command line, execute ‘find /Developer/ -iname symbolicatecrash’. grab the path and add it to your ~/.profile (if you are a bash kind of a guy). add this line: “PATH=/Developer/Platforms/iPhoneOS.platform/Developer/Library/PrivateFrameworks/DTDeviceKit.framework/ \
Versions/A/Resources/:$PATH” and don’t forget to “source ~/.profile” before you try and access the script.

tip #3:
enable malloc_error_break so xcode will halt when you double release an object or release a stomped memory. this directive for the debugger is actually a breakpoint. think about it, what we are asking xocde to do, is break on a memory allocation error as if it were a breakpoint (rather than crashing). this is very useful as the program will halt on the line of code that tried to perform the illegal action. add this to your project from the breakpoint view. easy as pie.

tip #4:
party with the zombies. edit your schema (xcode4 people can you hear me?) and add NSZombieEnabled = YES to the “environment variables” list. what happes here is fun. xcode will not release your objects when their reference count is zero, but will keep them for safekeep within the framework of the app. if any of the pseudo released objects is being sent a method, xcode will halt your application, load the debugger and point you to the line of code that tried to access what is suppose to be a zombie. how cool is that? caution! this method is a heavy memory foot print so take it under consideration when you enable them zombies to roam your lands.

on my next post i will show you a nifty header file that allows for fast turning on and off of debug calls from within your app.

good luck!