Compare version numbers in Objective-C

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? What options do I have to determine that "1.2.5" comes after "1.0.1"?

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
}

I'll add my method, which compares strictly numeric versions (no a, b, RC etc.) with any number of components.

+ (NSComparisonResult)compareVersion:(NSString*)versionOne toVersion:(NSString*)versionTwo {
    NSArray* versionOneComp = [versionOne componentsSeparatedByString:@"."];
    NSArray* versionTwoComp = [versionTwo componentsSeparatedByString:@"."];

    NSInteger pos = 0;

    while ([versionOneComp count] > pos || [versionTwoComp count] > pos) {
        NSInteger v1 = [versionOneComp count] > pos ? [[versionOneComp objectAtIndex:pos] integerValue] : 0;
        NSInteger v2 = [versionTwoComp count] > pos ? [[versionTwoComp objectAtIndex:pos] integerValue] : 0;
        if (v1 < v2) {
            return NSOrderedAscending;
        }
        else if (v1 > v2) {
            return NSOrderedDescending;
        }
        pos++;
    }

    return NSOrderedSame;
}

This is an expansion to Nathan de Vries answer to address the problem of 1 < 1.0 < 1.0.0 etc.

First off we can address the problem of extra ".0"'s on our version string with an NSString category:

@implementation NSString (VersionNumbers)
- (NSString *)shortenedVersionNumberString {
    static NSString *const unnecessaryVersionSuffix = @".0";
    NSString *shortenedVersionNumber = self;

    while ([shortenedVersionNumber hasSuffix:unnecessaryVersionSuffix]) {
        shortenedVersionNumber = [shortenedVersionNumber substringToIndex:shortenedVersionNumber.length - unnecessaryVersionSuffix.length];
    }

    return shortenedVersionNumber;
}
@end

With the above NSString category we can shorten our version numbers to drop the unnecessary .0's

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

requiredVersion = [requiredVersion shortenedVersionNumberString]; // now 1.2
actualVersion = [actualVersion shortenedVersionNumberString]; // still 1.1.5

Now we can still use the beautifully simple approach proposed by Nathan de Vries:

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

I made it myself,use Category..

Source..

@implementation NSString (VersionComparison)
- (NSComparisonResult)compareVersion:(NSString *)version{
    NSArray *version1 = [self componentsSeparatedByString:@"."];
    NSArray *version2 = [version componentsSeparatedByString:@"."];
    for(int i = 0 ; i < version1.count || i < version2.count; i++){
        NSInteger value1 = 0;
        NSInteger value2 = 0;
        if(i < version1.count){
            value1 = [version1[i] integerValue];
        }
        if(i < version2.count){
            value2 = [version2[i] integerValue];
        }
        if(value1  == value2){
            continue;
        }else{
            if(value1 > value2){
                return NSOrderedDescending;
            }else{
                return NSOrderedAscending;
            }
        }
    }
    return NSOrderedSame;
}

Test..

NSString *version1 = @"3.3.1";
NSString *version2 = @"3.12.1";
NSComparisonResult result = [version1 compareVersion:version2];
switch (result) {
    case NSOrderedAscending:
    case NSOrderedDescending:
    case NSOrderedSame:
         break;
    }