Question

Im having trouble understanding why the following code displays “The First Key = (null)” in the console/terminal:

Here is the Interface:

#import <UIKit/UIKit.h>

@interface TestingViewController : UIViewController

@property (nonatomic, strong) NSMutableArray *namesArray;
@property (nonatomic, strong) NSDictionary *myDictionary; 

@end

This is the implementation:

#import "DictionaryTestViewController.h"

@implementation DictionaryTestViewController

@synthesize namesArray;
@synthesize myDictionary;

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self.myDictionary initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];
    NSLog(@"The First Key = %@", [self.myDictionary objectForKey:@"key1"]);
}

@end

Thanks in advance!

Answer 1

You haven’t allocated your dictionary yet. It’s nil at the moment, and sending message to nil does nothing.

Change it to this instead if you’re using ARC

self.myDictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];

or this if not

self.myDictionary = [[[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil] autorelease];