Adding two integer numbers from array

Question

Imagine the following code:

    NSMutableArray *arr = [NSMutableArray arrayWithObjects:@200, @100, nil];
    
    NSInteger n1 = (NSInteger)[arr objectAtIndex:0];
    NSInteger n2 = (NSInteger)[arr objectAtIndex:1];
    NSInteger r = n1 + n2;
    
    NSLog(@"n: %lid", r);

The result I am getting is: -4309586476825365866d, the expected one is: 300.

I also tried to evaluate the individual expressions in debugger to check what I am getting when reading the values from the array, like this: po (NSInteger)[arr objectAtIndex:0]. This showed the correct number, yet when trying to sum them both: po (NSInteger)[arr objectAtIndex:0] + (NSInteger)[arr objectAtIndex:0], an invalid result is generated.

Any ideas why? I am very new to Objective-C, so any source where I could get more info about the issue is appreciated.

The NSArray can only hold objects: namely NSNumbers. -objectAtIndex: returns the pointer to the number; casting it to an NSInteger isn't what you want to do. Instead, use [[arr objectAtIndex:0] integerValue]; — NSGod
– NSGod, Commented Dec 25, 2021 at 21:28

vadian · Accepted Answer · 2021-12-25 21:35:23Z

1

You cannot cast NSNumber to NSInteger. You have to call integerValue.

And for more than 10 years there is a more convenient array literal syntax as well as a more convenient index subscription syntax

NSArray *arr = @[@200, @100];

NSInteger n1 = [arr[0] integerValue];
NSInteger n2 = [arr[1] integerValue];
NSInteger r = n1 + n2;

NSLog(@"n: %ld", r);

And for the string format use either i or d but not both.

answered Dec 25, 2021 at 21:35

vadian

286k32 gold badges378 silver badges379 bronze badges

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

Collectives™ on Stack Overflow

Adding two integer numbers from array

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related