NSArray's valueForKey is very convenient! :)

NSArray+objectForKeyedSubscript.m

#import <Foundation/Foundation.h>

@interface NSArray (objectForKeyedSubscript)

- (id)objectForKeyedSubscript:(id)key;

@end

@implementation NSArray (objectForKeyedSubscript)

- (id)objectForKeyedSubscript:(id)key
{
    return [[self valueForKey:key] firstObject];
}

@end

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

    @autoreleasepool {
        NSArray *ary = @[@{@"AAA": @"BBB"}];
        NSLog(@"%@", ary[@"AAA"]);
    }
    return 0;
}