我获取挂在七牛上的plist文件中的爸版本号，有的时候获取的结果不一样

NSDictionary* dict = [NSDictionary dictionaryWithContentsOfURL:[NSURL URLWithString:@"http://dn-xxxxxxxxx/HappyFaie-iphone.plist"]];

        NSArray* list = [dict objectForKey:@"items"];
    NSDictionary* dict2 = [list objectAtIndex:0];

    NSDictionary* dict3 = [dict2 objectForKey:@"metadata"];
    NSString* newVersion = [dict3 objectForKey:@"bundle-version"];

    NSString *myVersion = [NSString stringWithFormat:@"%@", [[NSBundle mainBundle] objectForInfoDictionaryKey:(NSString*)kCFBundleVersionKey]];
    NSLog(@"版本号%@=====%@",newVersion,myVersion);

    if (![newVersion isEqualToString:myVersion]) {

        UIAlertView * aler = [[UIAlertView alloc] initWithTitle:@"提示" message:@"发现新版本，是否更新？" delegate:self cancelButtonTitle:@"立即更新" otherButtonTitles:@"暂不更新", nil];
        [aler show];

    }

我用这段代码获取的版本号 有时候跟写在文件里的值不一样，请问有大神知道是为什么吗？