If you want to learn Cocoa… at Ole Begemann: iOS Development

If you want to learn Cocoa…

…be prepared to write a lot more code than in your typical “scripting” language. Three examples (I am using Ruby for comparison because it is the scripting language I am most familiar with; things would look very much the same with Python or PHP):

1. Declare a small hash/dictionary of key-value pairs

Ruby:

person = { 
  :name           => "John Appleseed", 
  :age            => 30, 
  :favorite_fruit => [ "apple", "banana", "kiwi" ]
}

Cocoa:

NSDictionary *person = [NSDictionary dictionaryWithObjectsAndKeys:
                        @"John Appleseed",               @"name",
                        [NSNumber numberWithInteger:30], @"age",
                        [NSArray arrayWithObjects:@"apple", @"banana", @"kiwi", nil],
                                                         @"favoriteFruit",
                        nil];

Now which of these is easier to read?

2. What day of the month is today?

Ruby:

today = Date.today                       # => #<Date: 4910525/2,0,2299161>
puts "Day of the month: %d" % today.day  # => Day of the month: 7

Cocoa:

NSDate *today = [NSDate date];                        // => 2010-03-07 15:15:26 +0100
NSCalendar *calendar = [NSCalendar currentCalendar];  // => <__NSCFCalendar: 0x100400160>
NSDateComponents *components = [calendar components:NSDayCalendarUnit
                                           fromDate:today];
NSLog(@"Day of the month: %d", [components day]);     // => Day of the month: 7

3. Fetch something from the data store

Ruby on Rails (Active Record):

result = Person.find(:all, :conditions => { :first_name => "John" }, :order => "created_at DESC")

Cocoa (Core Data):

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
 
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
 
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"firstName == %@", @"John"];
[fetchRequest setPredicate:predicate];
 
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"creationDate" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];
[sortDescriptor release];
 
NSError *fetchError = nil;
NSArray *fetchResult = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
[fetchRequest release];

Now I know this is not a fair comparison, Objective-C/Cocoa has many advantages over Ruby et al., you can’t compare Core Data to Active Record, etc. Still, I find the differences very striking, especially regarding the readability of the code.

Written by Ole Begemann

March 7th, 2010 at 3:59 pm

Posted in Uncategorized

2 Responses to 'If you want to learn Cocoa…'

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Wow, that was really helpful. That was the most informative thing I’ve ever read! I hope you can do more comparing Perl, C, Haskell, ADA, LISP, FORTRAN, and COBOL, too!

Thanks!

I'm impressed

16 Mar 10 at 12:23 am
^Previous poster.. don’t be so sarcastic… I really enjoy reading things like this, I tend to learn languages by building upon concepts I’ve learned elsewhere. As I’m familliar with Rails, I enjoy seeing how things are done in Cocoa.

Due to it being a compiled and memory managed language, it will obviously require more lines of code.. however the verbosity of Cocoa tends to aid it’s readability for me, and I have a pet peeve for strange abbreviations that other languages/frameworks tend to foster.
Xcode’s autocompletion makes it a non-issue.

Ryan

6 Apr 10 at 2:19 pm

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