比较两个版本字符串

Posted 2021-02-27

/*
 * compareVersions(@"10.4",             @"10.3")             returns NSOrderedDescending (1)
 * compareVersions(@"10.5",             @"10.5.0")           returns NSOrderedSame (0)
 * compareVersions(@"10.4 Build 8L127", @"10.4 Build 8P135") returns NSOrderedAscending (-1)
 */
NSComparisonResult compareVersions(NSString* leftVersion, NSString* rightVersion)
{
	int i;
 
	// Break version into fields (separated by '.')
	NSMutableArray *leftFields  = [[NSMutableArray alloc] initWithArray:[leftVersion  componentsSeparatedByString:@"."]];
	NSMutableArray *rightFields = [[NSMutableArray alloc] initWithArray:[rightVersion componentsSeparatedByString:@"."]];
 
	// Implict ".0" in case version doesn't have the same number of '.'
	if ([leftFields count] < [rightFields count]) {
		while ([leftFields count] != [rightFields count]) {
			[leftFields addObject:@"0"];
		}
	} else if ([leftFields count] > [rightFields count]) {
		while ([leftFields count] != [rightFields count]) {
			[rightFields addObject:@"0"];
		}
	}
 
	// Do a numeric comparison on each field
	for(i = 0; i < [leftFields count]; i++) {
		NSComparisonResult result = [[leftFields objectAtIndex:i] compare:[rightFields objectAtIndex:i] options:NSNumericSearch];
		if (result != NSOrderedSame) {
			[leftFields release];
			[rightFields release];
			return result;
		}
	}
 
	[leftFields release];
	[rightFields release];	
	return NSOrderedSame;
}