how to avoid NULL value in objective c

Question

Please consider this code:

 - (void)viewDidLoad
    {
        [super viewDidLoad];
        // Do any additional setup after loading the view from its nib.

        NSURL *url = [NSURL URLWithString:@"http://localhost/faq.php?faqType=2"]; // Modify this to 
        NSString *jsonreturn = [[NSString alloc] initWithContentsOfURL:url]; // Pulls the URL
        NSLog(@"jsonreturn=%@",jsonreturn); // Look at the console and you can see what the restults are
        NSData *jsonData = [jsonreturn dataUsingEncoding:NSUTF32BigEndianStringEncoding];
        NSError *error = nil;

        // In "real" code you should surround this with try and catch
        NSDictionary *dict = [[CJSONDeserializer deserializer] deserializeAsDictionary:jsonData error:&error];

        if (dict)
        {
            rows = [[dict objectForKey:@"faq"] retain];
        }
        [jsonreturn release];    
    }


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
  {

        // Configure the cell.
        static NSString *CellIdentifier = @"Cell";

        UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
        if (cell == nil) {
            cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier] autorelease];
        }

        NSDictionary *dict1 = [rows objectAtIndex:indexPath.row];
        NSLog(@"%@", dict1);
        cell.textLabel.text = [dict1 objectForKey:@"faqQues"];
  }


//if it is not getting NULL value then UItableView is ok
{"faq":[{"faqQues":"this is mr.mack?"},{"faqQues":"is he good man?"}]}

//but if the data is like NULL 

    {"faq":[{"faqQues":"this is mr.mack?"},{"faqQues":null}]}  // then it is creating EXEC_BAD_ACCESS error,

so how to avoid NULL or check null value, or how can i fix this issue?

Bill Burgess · Accepted Answer · 2011-12-01 18:35:21Z

2

You can query the value before using it.

if ([dict objectForKey:@"faqQues"] == [NSNull null]) {
    // value is null, use your own value here
} else {
    // good value to use
}

You can also do this while enumerating as well.

for (id value in dict) {
    if (value == [NSNull null]) {
        // null
    }

}

answered Dec 1, 2011 at 18:35

Bill Burgess

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Comments

Thomas Zoechling · Accepted Answer · 2011-12-01 18:38:47Z

0

The docs of TouchJSON state, that JSON null values are represented using the NSNull singleton (usually used to represent nil in collections - where nil is not allowed). So you have to check against [NSNull null].

But TouchJSON allows to override the default null object:

CJSONDeserializer *theDeserializer = [CJSONDeserializer deserializer];
theDeserializer.nullObject = NULL;

Details https://github.com/TouchCode/TouchJSON (see the "Avoiding NSNull values in output." section)

answered Dec 1, 2011 at 18:38

Thomas Zoechling

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Comments

Nate Symer · Accepted Answer · 2013-01-03 00:58:21Z

0

My fellow programmer Conrad Kramer actually came up with this: https://gist.github.com/3362607

I would change it to a function and replace NULL values with @""

answered Jan 3, 2013 at 0:58

Nate Symer

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