comapare version numbers in objective c

Question

hi, i am writing an application that receives data with items and version numbers. The numbers are formatted like 1.0.1 or 1.2.5. How can i compare these version numbers. I think they have to be formatted as a string first, no? If so, what option do i have to having objective C understand the 1.2.5 is newer than 1.0.1?

Answer 1

This question, while not identical to yours, offers insights on how you could accomplish what you're asking.

Answer 2

If you know each version number will have exactly 3 integers separated by dots, you can parse them (e.g. using sscanf(3)) and compare them:

const char *version1str = "1.0.1";
const char *version2str = "1.2.5";
int major1, minor1, patch1;
int major2, minor2, patch2;
if(sscanf(version1str, "%d.%d.%d", &major1, &minor1, &patch1) == 3 &&
   sscanf(version2str, "%d.%d.%d", &major2, &minor2, &patch2) == 3)
{
    // Parsing succeeded, now compare the integers
    if(major1 > major2 ||
      (major1 == major2 && (minor1 > minor2 ||
                           (minor1 == minor2 && patch1 > patch2))))
    {
        // version1 > version2
    }
    else if(major1 == major2 && minor1 == minor2 && patch1 == patch2)
    {
        // version1 == version2
    }
    else
    {
        // version2 < version2
    }
}
else
{
    // Handle error, parsing failed
}

Answer 3

Glibc has a function strverscmp and versionsort… unfortunately, not portable to the iPhone, but you can write your own fairly easily. This (untested) re-implementation comes from just reading the documented behavior, and not from reading Glibc's source code.

int strverscmp(const char *s1, const char *s2) {
    const char *b1 = s1, *b2 = s2, *e1, *e2;
    long n1, n2;
    size_t z1, z2;
    while (*b1 && *b1 == *b2) b1++, b2++;
    if (!*b1 && !*b2) return 0;
    e1 = b1, e2 = b2;
    while (b1 > s1 && isdigit(b1[-1])) b1--;
    while (b2 > s2 && isdigit(b2[-1])) b2--;
    n1 = strtol(b1, &e1, 10);
    n2 = strtol(b2, &e2, 10);
    if (b1 == e1 || b2 == e2) return strcmp(s1, s2);
    if (n1 < n2) return -1;
    if (n1 > n2) return 1;
    z1 = strspn(b1, "0"), z2 = strspn(b2, "0");
    if (z1 > z2) return -1;
    if (z1 < z2) return 1;
    return 0;
}

Answer 4

This is the simplest way to compare versions, keeping in mind that "1" < "1.0" < "1.0.0":

NSString* requiredVersion = @"1.2.0";
NSString* actualVersion = @"1.1.5";

if ([requiredVersion compare:actualVersion options:NSNumericSearch] == NSOrderedDescending) {
  // actualVersion is lower than the requiredVersion
}

Answer 5

Sparkle (a framework for MacOS) has a SUVersionComparator class that does this.