Question

I have an int currentFontSize where I wanna compare with NSString stored in an C array, here is the code.

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    static NSString* fontSizeName[] = 
    {
        @"14",
        @"18",
        @"22",
        @"26",
        @"30",
        @"34",
    };

    int fontSizeSegmentID;
    int currentFontSize = 22;

    NSString *val = [NSString stringWithFormat: @"%i", currentFontSize];
    NSString *val2 = @"22";
    NSLog(@"the current font size is %i", currentFontSize);
    NSLog(@"the current font Value1 is %i", val);
    NSLog(@"the current font Value2 is %i",val2);
    int i;
    for (i = 0; i < 6; i++) {

        NSLog(@"fontSizeNAme:%d",fontSizeName[i]);
        NSLog(@"val:%d",val);

            if (fontSizeName[i] == val) {
                NSLog(@"They are equal");
                fontSizeSegmentID = i;
                break;
            }

            NSLog(@"the fontSizeSegmentID is: %i" , fontSizeSegmentID);
        }

    [pool drain];
    return 0;
}

the strage part is , val give me a return value of 1879919632, which make my comparison failed. The strange part is when I hardcode the NSString as val2 = @”22″, the comparison become successful where val2 is: 4240, it’s the same as:

NSLog(@"fontSizeNAme:%d",fontSizeName[i]);

here is my return in NSLog:

2010-11-18 16:56:52.784 testINT[26034:a0f] the current font size is 22
2010-11-18 16:56:52.786 testINT[26034:a0f] the current font Value1 is 1879919632
2010-11-18 16:56:52.787 testINT[26034:a0f] the current font Value2 is 4240
2010-11-18 16:56:52.788 testINT[26034:a0f] fontSizeNAme:4176
2010-11-18 16:56:52.788 testINT[26034:a0f] val:1879919632
2010-11-18 16:56:52.788 testINT[26034:a0f] the fontSizeSegmentID is: 32767
2010-11-18 16:56:52.789 testINT[26034:a0f] fontSizeNAme:4208
2010-11-18 16:56:52.789 testINT[26034:a0f] val:1879919632
2010-11-18 16:56:52.790 testINT[26034:a0f] the fontSizeSegmentID is: 32767
2010-11-18 16:56:52.790 testINT[26034:a0f] fontSizeNAme:4240
2010-11-18 16:56:52.790 testINT[26034:a0f] val:1879919632
2010-11-18 16:56:52.791 testINT[26034:a0f] the fontSizeSegmentID is: 32767
2010-11-18 16:56:52.791 testINT[26034:a0f] fontSizeNAme:4272
2010-11-18 16:56:52.791 testINT[26034:a0f] val:1879919632
2010-11-18 16:56:52.792 testINT[26034:a0f] the fontSizeSegmentID is: 32767
2010-11-18 16:56:52.792 testINT[26034:a0f] fontSizeNAme:4304
2010-11-18 16:56:52.792 testINT[26034:a0f] val:1879919632
2010-11-18 16:56:52.793 testINT[26034:a0f] the fontSizeSegmentID is: 32767
2010-11-18 16:56:52.793 testINT[26034:a0f] fontSizeNAme:4336
2010-11-18 16:56:52.794 testINT[26034:a0f] val:1879919632
2010-11-18 16:56:52.794 testINT[26034:a0f] the fontSizeSegmentID is: 32767

Can anybody kindly explain me why? why I cast the @”22″ NString and the one form int returns a different value????? Thanks!

Answer 1

In Objective-C, you can’t just compare an int and NSString* which contains a string representation of an integer. To convert between the two, you need to do

NSString* s=@"11";
int i=[s intValue];  // i now contains 11

Also, the % specification in NSLog does not specify how you want the object to be interpreted. You need to specify the correct % thing matching with the type of the object. Otherwise it just shows you junk. So, both

NSLog(@"the current font Value1 is %i", val);
NSLog(@"the current font Value2 is %i",val2);

are illegal, because val and val2 are NSString*. Instead you need to do

NSLog(@"the current font Value1 is %@", val);
NSLog(@"the current font Value2 is %@",val2);

or

NSLog(@"the current font Value1 is %i", [val intValue]);
NSLog(@"the current font Value2 is %i",[val2 intValue]);

You can’t compare two NSString*s by == either. You need to use [aString isEqualTo:anotherString].