赫哥手打，喜欢就点赞下哈哈。
自己在做设置的时候遇到了问题，就是关于更新的，把自己的方法列一下。

这里先把你app的ID标进去：
http://itunes.apple.com/lookup?id=<Your app ID>
我先随机举例一个：

define APP_URL @"http://itunes.apple.com/cn/lookup?id=1093039842"

#pragma mark--检测版本号更新
-(void)checkVertion
{
     //检测更新
     AFHTTPRequestOperationManager *afManager = [AFHTTPRequestOperationManager manager];
     [afManager POST:APP_URL parameters:nil  success:^(AFHTTPRequestOperation * _Nonnull operation, id  _Nonnull responseObject)  {
          NSLog(@"%@",responseObject);
          /*responseObject是个字典{}，有两个key
           KEYresultCount = 1//表示搜到一个符合你要求的APP
           results =（）//这是个只有一个元素的数组，里面都是app信息，那一个元素就是一个字典。里面有各种key。其中有 trackName （名称）trackViewUrl = （下载地址）version （可显示的版本号）等等
           */
          //具体实现为
          NSArray *arr = [responseObject objectForKey:@"results"];
          NSDictionary *dic = [arr firstObject];
          NSString *versionStr = [dic objectForKey:@"version"];
          NSString *trackViewUrl = [dic objectForKey:@"trackViewUrl"];
          NSString *releaseNotes = [dic objectForKey:@"releaseNotes"];//更新日志
          
          //NSString* buile = [[NSBundle mainBundle] objectForInfoDictionaryKey: (NSString*) kCFBundleVersionKey];build号
          NSString* thisVersion = [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleShortVersionString"];
          if ([self compareVersionsFormAppStore:versionStr WithAppVersion:thisVersion]) {
               UIAlertController *alertVC = [UIAlertController alertControllerWithTitle:[NSString stringWithFormat:@"发现新版本:%@",versionStr] message:releaseNotes preferredStyle:UIAlertControllerStyleAlert];
               UIAlertAction *cancelAction  = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
                    NSLog(@"点击了取消");
               }];
               
               UIAlertAction *OKAction  = [UIAlertAction actionWithTitle:@"更新" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
                    NSLog(@"点击了知道了");
                    NSURL * url = [NSURL URLWithString:trackViewUrl];//itunesURL = trackViewUrl的内容
                    [[UIApplication sharedApplication] openURL:url];
               }];
               [alertVC addAction:cancelAction];
               [alertVC addAction:OKAction];
               [self presentViewController:alertVC animated:YES completion:nil];
          }
     } failure:^(AFHTTPRequestOperation * _Nonnull operation, NSError * _Nonnull error) {
          NSLog(@"");
     }];
}

//比较版本的方法，在这里用的是Version来比较的
- (BOOL)compareVersionsFormAppStore:(NSString*)AppStoreVersion WithAppVersion:(NSString*)AppVersion{
     
     BOOL littleSunResult = false;
     
     NSMutableArray* a = (NSMutableArray*) [AppStoreVersion componentsSeparatedByString: @"."];
     NSMutableArray* b = (NSMutableArray*) [AppVersion componentsSeparatedByString: @"."];
     
     while (a.count < b.count) { [a addObject: @"0"]; }
     while (b.count < a.count) { [b addObject: @"0"]; }
     
     for (int j = 0; j<a.count; j++) {
          if ([[a objectAtIndex:j] integerValue] > [[b objectAtIndex:j] integerValue]) {
               littleSunResult = true;
               break;
          }else if([[a objectAtIndex:j] integerValue] < [[b objectAtIndex:j] integerValue]){
               littleSunResult = false;
               break;
          }else{
               littleSunResult = false;
          }
     }
     return littleSunResult;//true就是有新版本，false就是没有新版本
}

最后在需要的地方引用
[self checkVertion];
取消再弄个提示就行了。