Having trouble adding objects to NSMutableArray

Question

Im having truble adding objects to my 2 NSMutableArrays. The data comes from a database and I know that my parsing is correct because I get valid outputs when I use the NSLog. However I can't figur out how to add the 2 different objects to my 2 different NSMutableArrays. Here is my code

-(void)connectionDidFinishLoading:(NSURLConnection *)connection {

     allDataDictionary = [NSJSONSerialization JSONObjectWithData:webData options:0 error:nil];
     feed = [allDataDictionary objectForKey:@"feed"];
     arrayOfEntry = [feed objectForKey:@"entry"];

     for (NSDictionary *dictionary in arrayOfEntry) {

         NSDictionary *title = [dictionary objectForKey:@"title"];
         NSString     *labelTitle = [title objectForKey:@"label"];

         [arrayLabel addObject:labelTitle];

         NSDictionary *summary = [dictionary objectForKey:@"summary"];
         NSString     *labelSummary = [summary objectForKey:@"label"]; 

         [arraySummary addObject:labelSummary]; //This line makes the application crash

     }

}

for some reason when I want to add labelSummary to arraySummary I get this error:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil'

Any help is appreciated.

What are your thoughts about the error message?

jscs
– jscs

2013-03-05 18:55:40 +00:00
Commented Mar 5, 2013 at 18:55 — jscs
– jscs, Commented Mar 5, 2013 at 18:55
I don't see a call to insertObject:atIndex:.

trojanfoe
– trojanfoe

2013-03-05 18:57:27 +00:00
Commented Mar 5, 2013 at 18:57 — trojanfoe
– trojanfoe, Commented Mar 5, 2013 at 18:57
@trojanfoe: addObject: calls through.

jscs
– jscs

2013-03-05 19:05:37 +00:00
Commented Mar 5, 2013 at 19:05 — jscs
– jscs, Commented Mar 5, 2013 at 19:05

TMacGyver · Accepted Answer · 2013-03-05 19:03:30Z

2

Your parsing is indeed correct. However, when the parser comes across an empty field it returns nil. The problem is the that NSArrays cannot accept nils, because nil is not an object, it's equivalent to 0. Therefore, you most add an object. This the role of NSNull.

Must test to see if the parser returns nil, and if so add [NSNull null].

NSString* labelSummary = [summary objectForKey:@"label"]; 

[arraySummary addObject:(labelSummary!=nil)?labelSummary:[NSNull null];

answered Mar 5, 2013 at 19:03

TMacGyver

1,2913 gold badges12 silver badges27 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

RockPaperScissors Over a year ago

You Rock! It worked! but how come I don't need to do that for lableTitle?

TMacGyver Over a year ago

@RockPaperScissors labelTitle didnt come back as nil. Its good practice to test all for nil after parsing, unless an error should be thrown for a nil value

Jean · Accepted Answer · 2013-03-05 19:07:45Z

1

The error message tells you that one of the objects you are trying to add to the array is nil.

You have to replace

[arrayLabel addObject:labelTitle];

with

if (labelTitle != nil) {
   [arrayLabel addObject:labelTitle];
}

and

[arraySummary addObject:labelSummary];

with

if (labelSummary != nil) {
   [arraySummary addObject:labelSummary];
}

If you really need to include a nil object, then use NSNull.

answered Mar 5, 2013 at 19:07

Jean

7,6816 gold badges46 silver badges58 bronze badges

Collectives™ on Stack Overflow

Having trouble adding objects to NSMutableArray

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related