How can I CORRECTLY append map array to firestore?-CodePudding

I want to add Map<> data to my firestore database with code :

Map<String, Object> prop = {
  'read' : true,
  'vote_left' : false,
  'vote_right' : false,
};
Map<String, Object> attended_topic =
{
  received_id:prop
};

FirebaseFirestore.instance.collection('userinfo').doc(user_now!.uid)
    .update({"attended_topic": FieldValue.arrayUnion([attended_topic])});

What I expected is this.

attended_topic
  topicId_0
    read : true 
    vote_left : false
    vote_right : false

But I got something unexpected.

attended_topic
  0
    topicId_0
      read : true 
      vote_left : false
      vote_right : false

I never expected that new category '0' appearing and donot know why. Since the atabase has other properties so I thought using update() rather than set() is adequate. Please somebody tell my why this happens.

CodePudding user response：

From the docs FieldValue.arrayUnion adds elements to an array but only elements not already present.

So {"a": FieldValue.arrayUnion([b])} adds b variable to the Array a.

To solve your problem, just remove FieldValue as shown below.

FirebaseFirestore.instance
    .collection('userinfo')
    .doc(user_now!.uid)
    .set({"attended_topic": attended_topic}, SetOptions(merge: true));
// use set method to add new data (not update)
// or

FirebaseFirestore.instance.collection('userinfo').doc(user_now!.uid).set(
  {
    'attended_topic': {
      received_id: {
        'read': true,
        'vote_left': false,
        'vote_right': false,
      }
    }
  },
  SetOptions(merge: true),
);

CodePudding user response：

I solved this problem referring Peter's solution and changing it slightly.

FirebaseFirestore.instance.collection('userinfo').doc(user_now!.uid)
    .set({"attended_topic": attended_topic}, SetOptions(merge: true));