arrays - 在 Flutter 中创建一个空数组并将其发送到带有空值的 Firestore？

Question

我想在发布提要时在 Firestore 中创建一个空数组。但是该数组在 Firestore 中显示为 null。这是我的代码。请帮忙。

   class FeedModel {
    
      final String imgUrl;
      final String desc;
      final String authorName;
      final String profileImg;
      final String title;
      final int likeCount;
      List<String> strArr = [];   // this the array i want to create it in firestore
    
      FeedModel({this.imgUrl, this.desc,this.authorName,this.profileImg,this.title,this.likeCount, this.strArr});
    
      Map<String, dynamic> toMap(){
        return {
         "imgUrl" : this.imgUrl,
          "desc" : this.desc,
          "authorName" : this.authorName,
          "profileImg" : this.profileImg,
          "like_count" : this.likeCount,
          "liked_user_id" : this.strArr
        };
      }
   
    }

发送数据代码如下:

Future<void> _sendData() async {

    try {
      final StorageReference firebaseStorageRef = FirebaseStorage.instance.ref().child('myimage.jpg');
      final StorageUploadTask task = firebaseStorageRef.putFile(_image);
      StorageTaskSnapshot taskSnapshot = await task.onComplete;
      String downloadUrl = await taskSnapshot.ref.getDownloadURL();
      final String pname = myController.text;
      final  String pimgurl = downloadUrl;
      final String pauthorName = "Sachin Tendulkar";
      final String pprofileImg = "https://i.picsum.photos/id/564/200/200.jpg?hmac=uExb18W9rplmCwAJ9SS5NVsLaurpaCTCBuHZdhsW25I";
      final String ptitle = "Demo Data";
      final int plikeCount= 0;
      List<String> pLikeduserId;  // This line returning null as show in image
      print(pimgurl);
      final FeedModel feeds = FeedModel(imgUrl: pimgurl ,desc: pname,authorName: pauthorName ,profileImg: pprofileImg,title: ptitle,likeCount: plikeCount, strArr : pLikeduserId );
      insertData(feeds.toMap());

    }  catch (e) {
      print(e);
    }

  }

空图像:

想要得到如下图:

创建 Feed 时如何像最后一张图片一样发送数组？

Answer 1

如果你想要一个字段中的数组，即使是一个空数组，你也必须给它分配一个实际的列表值。现在，通过根本不分配任何实际的列表值，您实际上是在为 liked_user_id 分配一个空值。

所以，只要给它一个值:

List<String> pLikeduserId = [];

这将写入一个空列表字段。