Dictionary Literals

Before Xcode 4.4 I didn't think I could write such strange things in Objective-C:

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])

{

    @autoreleasepool {

        NSMutableDictionary *test = [[NSMutableDictionary alloc]

                                     initWithDictionary: @{ @"key 1" : @"value 1", @"key 2" : @"value 2", @"key 3" : @"value 3" }];

        NSLog(@"test dictionary: %@", test);

        

        NSLog(@"key 2 = %@", test[@"key 2"]);

        test[@"key 2"] = @"value 2 changed";

        NSLog(@"changed test dictionary: %@", test);

        

        NSUInteger idx = 3;

        test[[NSString stringWithFormat:@"key %lu", idx]] = @"Hello, world!";

        NSLog(@"changed test dictionary: %@", test);

    }

    return 0;

}

Even this terrible line:

        test[[NSString stringWithFormat:@"key %lu", idx]] = @"Hello, world!";

works just fine: 

2012-09-22 11:22:06.569 TestDictionary[18727:303] test dictionary: {

    "key 1" = "value 1";

    "key 2" = "value 2";

    "key 3" = "value 3";

}

2012-09-22 11:22:06.571 TestDictionary[18727:303] key 2 = value 2

2012-09-22 11:22:06.571 TestDictionary[18727:303] changed test dictionary: {

    "key 1" = "value 1";

    "key 2" = "value 2 changed";

    "key 3" = "value 3";

}

2012-09-22 11:22:06.572 TestDictionary[18727:303] changed test dictionary: {

    "key 1" = "value 1";

    "key 2" = "value 2 changed";

    "key 3" = "Hello, world!";

}

More about Objective-C Literals:

  Objective-C Literals