How to store maps to a firestore array - arrays

Question

I have xyz document inside abc collection.
I want to add a map to an array inside document xyz.
I can add a single array item using this code
CollectionReference collection = this.collection(collection);
DocumentReference ref = collection.document(document);
ref.setData({"data": FieldValue.arrayUnion(values)});
here data is the parent array.
but when I try to add another map , firestore replace the values of index 0 , it does not add map to next index means to index 1,2,3 or .....
let see the example
here is the map
values = {
"tokens": "99",
"title": "Cleaning",
"location": {" lat": "34.4333", "lng": "53.4343"},
"id": "gVnGE5ZPRnQ8HYQq7dvT",
"client": "LFBXXj7Zi0xOr0FqBGID",
"date": "22/8/2019",
"message": "request message...",
"budget": "150",
"details": {
" When would you like to have the cleaners over?":
"week",
"What type of cleaning package would you prefer?":
"answer for the type of clean",
"Do you need the cleaning tools and materials?":
"false",
"What time do you prefer to have the cleaners over?":
"8/20/2019"
}
}
and I want to add it as new array item each time when I send data to the firestore
eg.
onTap() {
CollectionReference collection = this.collection(collection);
DocumentReference ref = collection.document(document);
ref.setData({"value": FieldValue.arrayUnion(values)});
}
here is the code
var values = {
"tokens": "99",
"title": "Cleaning",
"location": {" lat": "34.4333", "lng": "53.4343"},
"id": "gVnGE5ZPRnQ8HYQq7dvT",
"client": "LFBXXj7Zi0xOr0FqBGID",
"date": "22/8/2019",
"message": "request message...",
"budget": "150",
"details": {
" When would you like to have the cleaners over?":
"week",
"What type of cleaning package would you prefer?":
"answer for the type of clean",
"Do you need the cleaning tools and materials?":
"false",
"What time do you prefer to have the cleaners over?":
"8/20/2019"
}
}
onTap() {
CollectionReference collection = this.collection(collection);
DocumentReference ref = collection.document(document);
ref.setData({"value": FieldValue.arrayUnion(values)});
}

Answer 1

You are using setData function which overwrites your existing values. You need to use updateData function instead which will add the value to the existing array. Just change your onTap function to this:
onTap() {
CollectionReference collection = this.collection(collection);
DocumentReference ref = collection.document(document);
ref.updateData({"value": FieldValue.arrayUnion(values)});
}