Question

i’m pulling a 2 dimensional array from a remote server:

- (NSMutableArray*)qBlock{

NSURL *url = [NSURL URLWithString:@"http://wsome.php"];
NSError *error;
NSStringEncoding encoding;
NSString *response = [[NSString alloc] initWithContentsOfURL:url 
                                                usedEncoding:&encoding 
                                                       error:&error];
const char *convert = [response UTF8String];
NSString *responseString = [NSString stringWithUTF8String:convert];
NSMutableArray *sample = [responseString JSONValue];

return sample;
}

and putting them into:

NSMutableArray *qnBlock1 = [self qBlock];
NSString *answer1 = [NSString stringWithFormat:[[qnBlock1 objectAtIndex:0]objectAtIndex:1]];
answer = [[NSMutableDictionary alloc]init];
[answer setObject:answer1 forKey:@"1"];

question1.text = [[qnBlock1 objectAtIndex:0] objectAtIndex:0];
label1a.text = [[qnBlock1 objectAtIndex:0]objectAtIndex:2];
label1b.text = [[qnBlock1 objectAtIndex:0]objectAtIndex:3];
label1c.text = [[qnBlock1 objectAtIndex:0]objectAtIndex:4];
label1d.text = [[qnBlock1 objectAtIndex:0]objectAtIndex:5];

I received this error during runtime

-[__NSCFDictionary objectAtIndex:]: unrecognized selector sent to instance 0x6c179502012-04-30 09:43:50.794 AppName[371:f803] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFDictionary objectAtIndex:]: unrecognized selector sent to instance 0x6c17950'

Is this due to syntax issue for 2 dimensional array?

Answer 1

You’re not getting back a multi-dimensional array. You’re getting back an array of NSDictionary objects. The error you got indicates that you’re trying to send the message objectAtIndex: to an NSDictionary object, which fails since it has no such selector.

---

Update:

After chatting on the side, it became apparent that the following was true:

1. The user was using the SBJson library to parse the return value from his php web service.
2. The return value was either:
   • An NSDictionary with each key being the text representation of its (non-index-based) location in the list (@”1″, @”2″, etc…) and each value being an NSArray of NSString objects, or
   • An NSArray of NSString objects (seems to be the way a single “answer” returns)

Here’s the code I supplied to let him iterate through his return value:

NSURL *url = [NSURL URLWithString:@"{his url}"];
NSError *error;
NSStringEncoding encoding;
NSString *response = [[NSString alloc] initWithContentsOfURL:url usedEncoding:&encoding error:&error];
const char *convert = [response UTF8String];
NSString *responseString = [NSString stringWithUTF8String:convert];
NSLog(@"%@", responseString);
SBJsonParser *parser = [[SBJsonParser alloc] init];
id sample = [parser objectWithString:responseString];
if ([sample isKindOfClass:[NSDictionary class]]) {
    for (id item in sample) {
        NSLog(@"%@", [item description]);
        NSArray *subArray = [sample objectForKey:item]; // b/c I know it's an array
        for (NSString *str in subArray) {
            NSLog(@"item: %@", str);
        }
    }
} else if ([sample isKindOfClass:[NSArray class]]) {
    for (NSString *str in sample) {
        NSLog(@"item: %@", str);
    }
}

Hope it helps, J!