使用 getx 控制器时，未为类型“Rx<某个类>”定义 getter“某个变量”

我正在尝试为我的项目实施反应式 getx以实现更清晰的代码。

在控制器飞镖文件中，我有：

class ReadSinglePostController extends GetxController {
  var posts = Post(
          postID: 1,
          userID: 0,
          thumbnail: 'some base64string',
          imageList: 'some base64string',
          title: 'title',
          description: 'description',
          createdTime: DateTime.now())
      .obs;//initialization and make the class Post observable
  var postid = 0.obs; //initialize postid and make it observable
  void updateID(var postID) {
    postid = postID;
  } //update the postid variable when a specific post is clicked in the post list

  @override
  void onInit() {
    super.onInit();
    readPost(postid);
  }

  Future readPost(var postID) async {
    var result = await PostsDatabase.instance.readNote(postID);
    posts = result;
  }//function to read the detailed content of that specific post from database passing in the postid
}

然后在 UI 的主页上，我将所有帖子都放在一个网格中，我实现了这个控制器以在postid单击特定帖子时更新。单击帖子时，它会导航到帖子详细信息页面，并在该 UI 文件中出现错误：

Error:The getter "thumbnail" isn't defined for the type 'Rx<Post>'. 当我使用 getter 'title'、'description' 等时，会出现同样的错误。

这是代码：

class PostBody extends StatelessWidget {
  PostBody({
    Key? key,
  }) : super(key: key);

  final readSinglePostController = Get.put(ReadSinglePostController());

  @override
  Widget build(BuildContext context) {
    return DefaultTextStyle(
      style: Theme.of(context).textTheme.bodyText2!,
      child: LayoutBuilder(
        builder: (BuildContext context, BoxConstraints viewportConstraints) {
          return SingleChildScrollView(
            child: ConstrainedBox(
              constraints: BoxConstraints(
                minHeight: viewportConstraints.maxHeight,
              ),
              child: GetX<ReadSinglePostController>(
                builder: (controller) {
                  return ...
                              ...
                                ...
                                child: FadeInImage(
                                  placeholder: MemoryImage(kTransparentImage),
                                  image:
                                      Utility.imageFromBase64String(
                                              controller.posts.thumbnail)//Error:The getter "thumbnail" isn't defined for the type 'Rx<Post>'. and the same error comes up when I use getter 'title', 'description' and etc.
                                          .image,
                                ),...

有什么线索吗，伙计们？