Iphone sdk - Weird behavior when comparing NSNumber

Question

I have a project which does several network operations. For easy control I have given each operation a unique Id, defined as a NSNumber because i have to perform operations with objects and Array and is easier this way:

#define LOGIN_OPERATION                     [NSNumber numberWithInt:0]
#define REGISTER_USER_OPERATION             [NSNumber numberWithInt:1]
#define VERIFY_USER_OPERATION               [NSNumber numberWithInt:2]
#define REGISTER_USER_DATA_OPERATION        [NSNumber numberWithInt:3]
#define FORGOT_PASSWORD_OPERATION           [NSNumber numberWithInt:4]
#define PASSTIME_REGISTER_OPERATION         [NSNumber numberWithInt:5]
#define PASSTIME_VERIFY_TOKEN_OPERATION     [NSNumber numberWithInt:6]
#define PASSTIME_OPERATION                  [NSNumber numberWithInt:7]
#define SERVICES_OPERATION                  [NSNumber numberWithInt:8]
#define MAIL_SUPPORT_OPERATION              [NSNumber numberWithInt:9]
#define UPDATE_USER_INFO_OPERATION          [NSNumber numberWithInt:10]
#define OBTAIN_CACS_OPERATION               [NSNumber numberWithInt:11]
#define GET_PREPAID_BALANCE_OPERATION       [NSNumber numberWithInt:12]
#define UPDATE_SERVICES_OPERATION           [NSNumber numberWithInt:13]

then I simply used among my project instructions as the following, which has worked pretty well during the last year.

- (void) processNetworkResponseForOperation: (NSNumber*) opId {

    if (opId == SERVICES_OPERATION) {
        //do something
    } else if (opId == UPDATE_SERVICES_OPERATION) {
        //do something
    }

}

However today i added the last operation (number 13) and all the == operations result false, just with that number!, i have used the debugger to assure that the value is ok, but i can only get the condition to true if I use: [opId isEqualToNumber: UPDATE_SERVICES_OPERATION] which is pretty long.

I understand that NSNumber is an object and thus == may not be the best choise, but why does it works with all other operations among the project but with #13 wont work?

Any help will be appreciated.

Edit Well i tried with bigger numbers and i have the same problem, but for example if I switch theUPDATE_SERVICES_OPERATION number with another op number, it now does the UPDATE_SERVICES_OPERATION but it wont do the operation which i switched the number. So why doesn't it work with newer numbers :S, or is it just a build problem on xcode? (i will restart and update)

Answer 1

You should never compare an NSNumber directly like you are doing here because it is an object and not a simple type. Your current code is depending on the equality of the objects memory addresses not their value. Read here for more information Comparing objects in Obj-C.

You should never use == to compare for object equality but instead the isEqual: function on NSObject and usually only if you want to be sure the objects you are comparing are the same instance. The code below should fix your problem.

- (void) processNetworkResponseForOperation: (NSNumber*) opId {

    if ([opId intValue] == [SERVICES_OPERATION intValue]) {
        //do something
    } else if ([opId intValue] == [UPDATE_SERVICES_OPERATION intValue]) {
        //do something
    }

}