iOS比较app版本号大小

- (NSComparisonResult)compare:(NSString *)appVersion currentVersion:(NSString *)currentVersion
{
    
    
    NSArray *appVerNums  = [appVersion componentsSeparatedByString:@"."];
    NSArray *currentVerNums = [currentVersion componentsSeparatedByString:@"."];
    for (NSInteger i = 0; i < appVerNums.count; i ++) {
    
    
        NSInteger appNum = [appVerNums[i] integerValue];
        if (i < currentVerNums.count) {
    
    
            NSInteger currentNum = [currentVerNums[i] integerValue];
            if (appNum < currentNum) {
    
    
                return NSOrderedAscending;
            } else if (appNum > currentNum) {
    
    
                return NSOrderedDescending;
            }
        }
    }
    if (appVerNums.count > currentVerNums.count) {
    
    
        return NSOrderedDescending;
    } else if (appVerNums.count < currentVerNums.count) {
    
    
        return NSOrderedAscending;
    }
    return NSOrderedSame;
}