Cocoa Kucha talk at @NSLondonMeetup about iOS backports. Whats that, why you should use them and example of base internationalisation backport to iOS5 #1 I am iOS developer from before official iOS SDK times and I have seen how it grow and evolves #2 Time to time Apple release new version of iOS SDK. All those new features that will open up new possibilities #3 But those other people - you know - like your boss for example, doesn’t understand that time you will waste to support multiple iOS versions will be more expensive than those 3 users that still didn’t updated #4 So you stuck for a few years supporting 2 or 3 versions of SDK writing spaghetti code, checking if class or method exist to use different code paths #5 Backports to the rescue! No spaghetti code, no checking for methods or class existence, no impact on users who already updated #6 Good backport is a runtime hook and have no implications on SDK’s that supports functionality natively #7 It’s not that hard to implement if you know what you doing and it will make your app code way cleaner and more maintainable in a long term #8 Can everything be backported? Most likely yes, but sometimes it could be more complex than the app itself and it would be a waste of time. On the other hand it could be few lines of code and could do things that would be extremely difficult to do otherwise #9 I made few of those, maybe you used some, maybe not, but nevertheless I think it’s insanely cool, and I use them in apps I write #10 For example, base internationalisation backport. You know - that small checkbox in Xcode that makes you life as developer way brighter if you making multilingual applications #11 If you launch App on iOS5 witch doesn’t support base internationalisation you will see NSUnarchyver error that NSLocalizableString doesn’t exist #12 Fortunately NSKeyedUnarchiver has convenient method to replace classes #13 Next, you have to extract info passed into -[RRLocalizableString initWithCoder:]. There is no easy way to find out -[NSCoder decodeObjectForKey:] keys, but the best way I found is to swizzle it #14 NSString belongs to class cluster... #15 by swizzling -[NSCoder decodeObjectForKey:] you will find NSKey and NSDev to use in -[NSBundle localizedStringForKey:value:table:], but we still missing “table”. #16 Unfortunately there is no public method on NSCoder to wind out what file we unarchiving #17 Most file operations use -[NSBundle pathForResource:ofType:] and sure enough swizzling it gives path we need. All we have to do is store it #18 There is several ways to store information in categories #19 All what was needed to make this complicated looking backport was several lines of code #20 there is no reason to write hard maintainable code just to support older SDK’s, so I invite everyone to check out my backports on github and write some of their own

1. BACKPORTS
Rolandas Razma
image: Holger

2. image: Audi

3. image: Jenny

4. image: ken

5. BACKPORTS

8. image: Michael
image:

10. SMALL
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12. [NSKeyedUnarchiver setClass: [RRLocalizableString class]
forClassName: @"NSLocalizableString"];
image: Angela

13. image: Johan Wieland

14. image: European Southern Observatory

15. - (id)initWithCoder:(NSCoder *)aDecoder {
if( (self = [super init]) ){
_stringsFileKey
= [aDecoder decodeObjectForKey:@"NSKey"];
_developmentLanguageString = [aDecoder decodeObjectForKey:@"NSDev"];
}
}
return self;
- (id)awakeAfterUsingCoder:(NSCoder *)aDecoder {
return [[NSBundle mainBundle] localizedStringForKey: _stringsFileKey
value: _developmentLanguageString
table: ??currentNibName??];
}
image: Don J Schulte

16. image: Tom Gill

17. -[NSBundle pathForResource:ofType:]

18. image: Dan Iggers

19. - (id)initWithCoder:(NSCoder *)aDecoder {
if( (self = [super init]) ){
_stringsFileKey
= [aDecoder decodeObjectForKey:@"NSKey"];
_developmentLanguageString = [aDecoder decodeObjectForKey:@"NSDev"];
}
return self;
}
- (id)awakeAfterUsingCoder:(NSCoder *)aDecoder {
return [[NSBundle mainBundle] localizedStringForKey: _stringsFileKey
value: _developmentLanguageString
table: [NSBundle currentNibName]];
}

20. rolandas@razma.lt
@rolandas_razma
github.com/rolandasrazm
a