NSMutableArray does not return value and assign to variable

Question

I have an NSMutableArray in my code and I want to access the last element of that array and save the element in integer n variable. But n does not give me the correct value when I NSLog it, it gives me a garbage value.

 for(int i=0;i<[array3 count];i++)
    {
        if(i==([array3 count]-1))
        {
            n = [array3 objectAtIndex:i];
        }    
    }

    NSLog(@"The id is=%d",n);

    NSError *error;
    NSString *aDocumentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
        NSString *dataPath = [aDocumentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%d",n]];
      [[NSFileManager defaultManager] createDirectoryAtPath:dataPath withIntermediateDirectories:NO attributes:nil error:&error];

If n is type int, it would not work. Because array only holds object and int is not object. — user523234
– user523234, Commented Jul 18, 2013 at 16:30
You can't store int in an NSMutableArray directly. Paste the code where you are adding objects — Midhun MP
– Midhun MP, Commented Jul 18, 2013 at 16:34

danh · Accepted Answer · 2013-07-18 16:36:05Z

3

Arrays contain objects, not scalar types like ints. Try this instead:

id n = [array3 lastObject];          // prettier than objectAtIndex:[array count]-1
NSLog(@"the last object is %@", n);   // %@ is an object format descriptor

Maybe the array contains NSNumbers that make sense as integers? Then,

NSNumber *n = [array3 lastObject];
NSLog(@"the last object is %@ or view it this way %d", n, [n intValue]);

You can also access an array with newer syntax like this:

id n = array3[array3.count-1];

You can also iterate an array more quickly and concisely like this:

for (id object in array3) {
    NSLog(@"%@", object);
}

edited Jul 18, 2013 at 16:36

answered Jul 18, 2013 at 16:30

danh

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3 Comments

Nasir Over a year ago

sir, what is "id" mean what is its type?

Tim Over a year ago

An id is an objective-c keyword that is 'some kind of object', see developer.apple.com/library/ios/#documentation/cocoa/conceptual/…

danh Over a year ago

id is the objective c generic type, like void* in c. You probably ought to figure out what type(s) is really contained by the array and code for that.

Stakenborg · Accepted Answer · 2013-07-18 16:36:40Z

0

It's giving you a garbage value because you're trying to cast an object to a primitive most likely.

Also, that for loop is unnecessary.

n = [[array3 lastObject] integerValue];

Should be everything you need. If that is still garbage, it's because the object in your array is garbage (or can't be cast to an integer). At that point, take a look at where you're setting up array3.

answered Jul 18, 2013 at 16:36

Stakenborg

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1 Comment

HAS Over a year ago

Since OP uses %d in his NSLog() I assume he uses int and not NSInteger, so would call intValue instead of integetValue ;)

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