Loop For

Today I found a wonderful blog: Able Pear Software. Here is first two posts I read there:
1. Objective-C Tuesdays: The for loop
2. Objective-C Tuesdays: for loop variations
Sure, the subject is trivial. But the explanation is perfect. Simple and clear.
Next tutorial Objective-C Tuesdays: The for...in loop shows new things. For example, the following program uses an enumerator to print out the elements of NSSet:

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    NSSet *items = [NSSet setWithObjects:@"foo", @"bar", nil];
    NSEnumerator *enumerator = [items objectEnumerator];
    NSString *item = nil;
    while (item = [enumerator nextObject]) {
        NSLog(item);
    }
    
    [pool drain];
    return 0;
}

The program output looks so:

[Session started at 2010-03-11 22:26:59 +0200.]
2010-03-11 22:27:00.008 Enumerator[4905:903] foo
2010-03-11 22:27:00.014 Enumerator[4905:903] bar

The Debugger has exited with status 0.

For NSArray it is obviously to use for-loop. NSSet does not have a well defined order, so NSEnumerator used to be the only option. Now, the same task can be solved with for..in-loop:

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    NSSet *items = [NSSet setWithObjects:@"foo", @"bar", nil];
    NSString *item = nil;
    for (item in items) {
        NSLog(@"item = %@", item);
    }
    
    [pool drain];
    return 0;
}

Same with NSArray:

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    NSArray *collection = [NSArray 
                           arrayWithObjects:@"foo", @"a", @"bar", @"baz", nil];
    for (NSUInteger i = 0; i < collection.count; i++) {
        NSString *item = [collection objectAtIndex:i];
        NSLog(@"item '%@'", item);
    }
    [pool drain];
    return 0;
}

And with the for..in loop:

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    NSArray *collection = [NSArray 
                           arrayWithObjects:@"foo", @"a", @"bar", @"baz", nil];
    for (NSString *item in collection) {
        NSLog(@"item '%@'", item);
    }
    [pool drain];
    return 0;
}