How to count string in an List with Firebase Flutter-CodePudding

I have an list of string in List. But I want to count it and display it in the text. How can I achieve that?

         StreamBuilder<DocumentSnapshot?>(
                  stream: FirebaseFirestore.instance
                      .collection("groups")
                      .doc(groupId)
                      .snapshots(),
                  builder: (context, snapshot) {
                   //Get a snapShot
                    var countRoom = snapshot.data?['room'];
                    //Display a counted room
                    return Text(countRoom)
                   )
                 }

CodePudding user response：

I want to count it (the list)

If I correctly understand your question, you need to use the length property as follows:

var countRoom = snapshot.data?['room'];
var countRoomLength = countRoom.length;

If you want to count the unique elements in the List, see this SO answer.

CodePudding user response：

If you want sum of the string in your list you can do this:

var rooms = snapshot.data?['room'];
int countRoom = rooms.fold(0, (int previousValue, element) => previousValue   int.parse(element));

return Text("$countRoom")//show 2

CodePudding user response：

To count the number of occurrences of a string in a list in Flutter using Firebase, you can use the where() method of the FirebaseFirestore class to filter the list and the length property to count the number of elements that meet the specified criteria.

Here's an example of how you can do this:

import 'package:firebase_firestore/firebase_firestore.dart';

// Assume that you have a list of strings called 'items'
// and a Firebase Firestore instance called 'firestore'

// Define the string you want to count the occurrences of
String targetString = 'example';

// Use the where() method to filter the list by the target string
var query = firestore.collection('items').where('name', isEqualTo: targetString);

// Use the get() method to execute the query and get the results
query.get().then((snapshot) {
  // Use the length property to count the number of elements in the snapshot
  int count = snapshot.docs.length;
  print('Number of occurrences of $targetString: $count');
});

This code will count the number of elements in the 'items' collection that have a 'name' field equal to the 'targetString'. The results of the query are returned as a QuerySnapshot object, which contains a list of documents in the docs property. You can use the length property of this list to count the number of documents that meet the specified criteria.

I hope this helps! Let me know if you have any questions.