What’s new(ish) in ObjectiveC

An overview of various syntax and compiler improvements that appeared in ObjC in the last few years, which make the code simpler and more DRY. Most of these were made possible by switching from GCC to Apple's own compiler infrastructure (LLVM). This includes:

* automatic generation of instance variables for @properties
* blocks (closures, lambdas)
* possibility to declare private instance variables in *.m file
* ARC (Automatic Reference Counting)
* automatic forward method declarations
* automatic @synthesize for @properties
* ObjC literals and array/dictionary subscripting

Two useful additions to Foundation.framework are also mentioned:

* NSJSONSerialization for JSON parsing
* NSRegularExpression for matching strings with regular expressions

Transcript

1. What’s new(ish) in ObjectiveC
   Kuba Suder
   @psionides • jsuder • http://psionides.eu • Lunar Logic
   

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2. Confession: I’m a Rubyist
   

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3. Ruby is awesome
   class Post
   belongs_to :user
   end
   Post.where('created_at > ?', date).order(‘title’)
   

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4. ObjC sometimes makes me cry
   NSManagedObjectContext * context = [[NSApp delegate] managedObjectContext];
   NSManagedObjectModel * model = [[NSApp delegate] managedObjectModel];
   NSDictionary * entities = [model entitiesByName];
   NSEntityDescription * entity = [entities valueForKey:@"Post"];
   NSPredicate * predicate;
   predicate = [NSPredicate predicateWithFormat:@"creationDate > %@", date];
   NSSortDescriptor * sort = [[NSSortDescriptor alloc] initWithKey:@"title"];
   NSArray * sortDescriptors = [NSArray arrayWithObject: sort];
   NSFetchRequest * fetch = [[NSFetchRequest alloc] init];
   [fetch setEntity: entity];
   [fetch setPredicate: predicate];
   [fetch setSortDescriptors: sortDescriptors];
   NSArray * results = [context executeFetchRequest:fetch error:nil];
   [sort release];
   [fetch release];
   

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5. ObjC sometimes makes me cry
   NSManagedObjectContext * context = [[NSApp delegate] managedObjectContext];
   NSManagedObjectModel * model = [[NSApp delegate] managedObjectModel];
   NSDictionary * entities = [model entitiesByName];
   NSEntityDescription * entity = [entities valueForKey:@"Post"];
   NSPredicate * predicate;
   predicate = [NSPredicate predicateWithFormat:@"creationDate > %@", date];
   NSSortDescriptor * sort = [[NSSortDescriptor alloc] initWithKey:@"title"];
   NSArray * sortDescriptors = [NSArray arrayWithObject: sort];
   NSFetchRequest * fetch = [[NSFetchRequest alloc] init];
   [fetch setEntity: entity];
   [fetch setPredicate: predicate];
   [fetch setSortDescriptors: sortDescriptors];
   NSArray * results = [context executeFetchRequest:fetch error:nil];
   [sort release];
   [fetch release];
   

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6. LLVM to the rescue!
   

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7. Instance variables for @property
   Requires: modern runtime(*)
   

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8. (*) WTF is modern runtime?
   

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9. (*) WTF is modern runtime?
   • “non-fragile variables”
   

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10. (*) WTF is modern runtime?
    • “non-fragile variables”
    • iOS
    

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11. (*) WTF is modern runtime?
    • “non-fragile variables”
    • iOS
    • OSX 10.5+ (64-bit)
    

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12. Instance variables for @property
    Before:
    // MyKlass.h
    @interface MyKlass {
    NSMutableArray *list;
    }
    @property NSMutableArray *list;
    @end
    

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13. Instance variables for @property
    After:
    // MyKlass.h
    @interface MyKlass
    @property NSMutableArray *list;
    @end
    

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14. Blocks (closures)
    OSX 10.6 / iOS 4.0
    

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15. Blocks
    // calling
    [list enumerateObjectsUsingBlock: ^(id obj, NSUInteger i, BOOL *stop) {
    NSLog(@”#%d = %@”, i, obj);
    }];
    // declaring
    - (void) connectTo: (NSString *) url
    callback: (void (^)(NSString *)) callback {
    NSString *response = [connector requestTo: url];
    callback(response);
    }
    

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16. Private variables
    Xcode 4.2 + LLVM + modern runtime
    

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17. Private variables
    Before - variables in a header file:
    // MyKlass.h
    @interface MyKlass {
    NSMutableArray *list;
    }
    @end
    (@protected by default)
    

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18. Private variables
    Xcode 4 + LLVM - class extension:
    // MyKlass.m
    @interface MyKlass () {
    NSMutableArray *list;
    }
    @end
    

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19. Private variables
    Xcode 4.2 + LLVM:
    // MyKlass.m
    @implementation MyKlass {
    NSMutableArray *list;
    }
    @end
    

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20. Automatic Reference Counting
    Xcode 4.2 + OSX 10.6 64-bit / iOS 4.0
    

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21. ARC
    Before:
    - (NSArray *) views {
    NSMutableArray *arr = [[NSMutableArray alloc] init];
    UIView *view = [[UIView alloc] initWithFrame: frame];
    [arr addObject: view];
    [view release];
    return [arr autorelease];
    }
    

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22. ARC
    After:
    - (NSArray *) views {
    NSMutableArray *arr = [[NSMutableArray alloc] init];
    UIView *view = [[UIView alloc] initWithFrame: frame];
    [arr addObject: view];
    // view magically released
    return arr;
    // arr magically autoreleased
    }
    

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23. ARC
    Before:
    - (void) dealloc {
    [window release];
    [panel release];
    [notifier unsubscribe: self];
    [super dealloc];
    }
    

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24. ARC
    After:
    - (void) dealloc {
    // window and panel magically released
    [notifier unsubscribe: self];
    // [super dealloc] is actually forbidden
    }
    

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25. ARC
    Before:
    NSAutoreleasePool *pool =
    [[NSAutoreleasePool alloc] init];
    // ...
    [pool drain];
    

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26. ARC
    After:
    @autoreleasepool {
    // ...
    }
    

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27. ARC
    Before:
    @property (retain) NSWindow *window;
    After:
    @property (strong) NSWindow *window;
    

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28. ARC
    Before:
    @property (assign) id delegate;
    After:
    @property (unsafe_unretained) id delegate;
    Or better (OSX 10.7 / iOS 5) - set to nil when object is released:
    @property (weak) id delegate;
    

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29. ARC
    • calling dealloc, retain, release, autorelease or
    retainCount is verboten
    • you have to follow the rules
    • using CFCreateThingie() requires extra keywords/wrapping
    • can be enabled/disabled per file
    

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30. GC: deprecated in OSX 10.8
    

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31. Forward method declarations
    Xcode 4.3
    

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32. Forward method declarations
    Problem:
    @implementation MyKlass
    - (void) bar {
    [self foo]; // <-- Xcode: wtf is this
    }
    - (void) foo {
    }
    @end
    

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33. Forward method declarations
    Before:
    @interface MyKlass ()
    - (void) foo;
    @end
    @implementation MyKlass
    - (void) bar {
    [self foo];
    }
    // ...
    

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34. Forward method declarations
    After:
    // yay, no @interface!
    @implementation MyKlass
    - (void) bar {
    [self foo];
    }
    - (void) foo {
    }
    @end
    

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35. Automatic @synthesize
    Xcode 4.4 + modern runtime
    

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36. Automatic @synthesize
    Before:
    @interface MyKlass
    @property NSString *name;
    @end
    @implementation MyKlass
    @synthesize name;
    - (void) printName {
    NSLog(@”%@ %@”, name, self.name);
    }
    @end
    

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37. Automatic @synthesize
    After:
    @interface MyKlass
    @property NSString *name;
    @end
    @implementation MyKlass
    - (void) printName {
    NSLog(@”%@ %@”, _name, self.name);
    }
    @end
    

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38. ObjC literals
    Xcode 4.4
    

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39. Literals
    Before:
    [NSNumber numberWithBool: YES]
    [NSNumber numberWithInt: 1]
    [NSNumber numberWithFloat: x]
    After:
    @1, @2.5, @YES, @(x)
    

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40. Literals
    Before:
    [NSArray arrayWithObjects: @”twitter”, @”facebook”,
    @”github”, nil]
    [NSDictionary dictionaryWithObjectsAndKeys: @”Kuba”,
    @”firstName”, @”Suder”, @”lastName”, [NSNumber
    numberWithInt: 30], @”age”, nil]
    

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41. Literals
    Before:
    [NSArray arrayWithObjects: @”twitter”, @”facebook”,
    @”github”, nil]
    [NSDictionary dictionaryWithObjectsAndKeys: @”Kuba”,
    @”firstName”, @”Suder”, @”lastName”, [NSNumber
    numberWithInt: 30], @”age”, nil]
    

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42. Literals
    After:
    @[@”twitter”, @”facebook”, @”github”]
    @{ @”firstName”: @”Kuba”, @”lastName”: @”Suder”,
    @”age”: @30 }
    

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43. Array & dictionary subscripting
    Xcode 4.4 + OSX 10.6 modern runtime / iOS 5
    

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44. Subscripting
    Before:
    [array objectAtIndex: 2]
    [array replaceObjectAtIndex: 0 withObject: @”first”]
    After:
    array[2]
    array[0] = @”first”
    

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45. Subscripting
    Before:
    [dictionary objectForKey: @”id”]
    [dictionary setObject: @”jsuder” forKey: @”author”]
    After:
    dictionary[@”id”]
    dictionary[@”author”] = @”jsuder”
    

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46. Subscripting
    Make your own array!
    - (id) objectAtIndexedSubscript: (NSUInteger) i {
    return list[i];
    }
    NSLog(@”record = %@”, collection[5]);
    

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47. Subscripting
    Make your own dictionary!
    - (id) objectAtKeyedSubscript: (id) key {
    for (Node *node in tree) {
    if ([node.name isEqual: key]) return node;
    }
    return nil;
    }
    NSLog(@”node = %@”, xmlDocument[@”date”]);
    

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48. Works on iOS 4.3 with libarclite
    http://petersteinberger.com/blog/2012/using-subscripting-with-Xcode-4_4-and-iOS-4_3/
    

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49. Extras from Foundation
    

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50. JSON parsing
    OSX 10.7 / iOS 5.0
    

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51. JSON parsing
    Before:
    TouchJSON / YAJL / JSON Framework / JSONKit / ...
    After:
    [NSJSONSerialization JSONObjectWithData: data
    options: 0
    error: &err];
    

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52. Regular expressions
    OSX 10.7 / iOS 4.0
    

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53. Regular expressions
    Before:
    RegexKit / RegexKitLite
    After:
    NSString *pattern = @”^\\w+@\\w+(\\.\\w+)+$”;
    NSRegularExpression *re =
    [NSRegularExpression regularExpressionWithPattern: pattern
    options: 0
    error: &err];
    [re matchesInString: email options: 0 range: NSMakeRange(0,20)];
    

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54. Sources
    • https://developer.apple.com
    • http://stackoverflow.com
    • https://developer.apple.com/library/ios/#releasenotes/
    ObjectiveC/ObjCAvailabilityIndex/
    • Google :)
    

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