How to update a Firestore document after querying in Flutter - flutter

Question

I am trying to figure out how to update my document after I query the one I want to update. Here is the code I came up with:
Firestore.instance.collection("Social_Posts").where(data["postTitle"], isEqualTo: "postTitle").where(data["postContent"], isEqualTo: "postContent")
.snapshots()
.listen((event) {print("hh");});
Whenever I perform this query to find the correct document, I would like to update the document by adding a number to it.

Answer 1

It is possible to update the document from inside, The easier way to do that would definitely be to use the documentID and to increment the value Firestore has a special property, FieldValue.increment(1). Using this you can easily increment a field.
Lets say the field in the document you want to increment by 1, is "numberField".
Updated code using async/await style:
onTap: () async {
setState(() {
_title = data["postTitle"];
_content= data["postContent"];
});
print(_title);
print(_content);
QuerySnaphot snapshot = await Firestore.instance.collection("Social_Posts")
.where("postTitle" , isEqualTo: _title)
.where("postContent", isEqualTo: _content)
.getDocuments();
if(snapshot.documents.isNotEmpty)
{
snapshot.documents.forEach((doc){
doc.reference.updateData({"views" : FieldValue.increment(1),});
});
}
}
The numberField will be incremented without needing to make an extra call to know the present value.
EDIT : You were making a mistake in the .where() method

Answer 2

You can do that by using the document id you quired from inside the listen function in your case by using the event.documents[0].documentID assuming that your query returns one document only and then you can call the updateData method from Firestone package
Your code might looks like this:
Firestore.instance.collection("Social_Posts")
.where(data["postTitle"], isEqualTo: "postTitle")
.where(data["postContent"], isEqualTo: "postContent")
.snapshots()
.listen((event) {
Firestore.instance
.collection("Social_Posts")
.document(
event.documents[0].documentID)
.updateData(
updateEvent) //Add here the new object you want to
.whenComplete(() {
// You can add your desire action after the row is updated
}
});
You can check package page for more information https://pub.dev/packages/cloud_firestore
And if you want to check a sample on how to perform CRUD functionalities you can check this repository: https://github.com/sayed3li97/flutter_firestore_crud