Objective C Arithmetic failing

Question

I have a NSNumber and when I try to do basic arithmetic it fails.

NSNumber *contentExpirationInDays = [NSNumber numberWithInt: 1];

When I try to do a basic multiplication to convert to seconds it gives me crazy numbers:

NSTimeInterval contentExpirationInSecs =  [contentExpirationInDays intValue] * 24 * 60 * 60;

Note: The next bit is now irrelevant as explained in some answers:

When I run the following commands in the console I get the following results:

(lldb) po [contentExpirationInDays intValue]
1

(lldb) po [contentExpirationInDays intValue] * 2
-148319360

UPDATE

Thanks for the information regarding po vs p. I didn't know that detail...

So here is the real problem that I am experiencing:

NSNumber *contentExpirationInDays = [[NSNumber numberWithInt:1];
NSTimeInterval contentExpiration = ([contentExpirationInDays intValue] * 24 * 60 * 60);
myObj.expirationDate = [[NSDate date] dateByAddingTimeInterval:contentExpiration];

obj.expirationDate usually ends up with many years in the future or many years in the past instead of one day ahead of today.

`po` is "print object". Use `p` to print integers or other scalar values. — Martin R, Sep 27 '16 at 00:02
What version of Xcode are you using? Works perfectly fine on my Xcode 8. — Mobile Ben, Sep 27 '16 at 02:27
This works for me, too, if I remove the extra `[` after the assignment (`=`) in the first line. However, the date calculation is a little bit naive. — Amin Negm-Awad, Sep 28 '16 at 02:39

score 1 · Answer 1 · answered Sep 27 '16 at 06:32

1

po is asking the debugger to print the description of the object at the address specified by the given pointer. As Martin R said, use p instead for just printing out scalar values:

p [contentExpirationInDays intValue] * 2

answered Sep 27 '16 at 06:32

norders

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score -1 · Answer 2 · answered Sep 27 '16 at 01:54

-1

NSNumber is a base class for objects which represent numbers, not a primitive scalar value such as a int or float.

If you need your number as an object, use NSDecimalNumber instead. Otherwise just leave it as a scalar type.

answered Sep 27 '16 at 01:54

drekka

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He converts it to a scalar using `-intValue`. – Amin Negm-Awad Sep 27 '16 at 05:50

Objective C Arithmetic failing

2 Answers2