Query collection and filter the results by field items

Hi folks,

I'm building a fitness app, where I have a collection of documents, each document is an exercise with name, description... and muscle groups. What I want to achieve, is to query every documents, list it by muscle groups only, but list each muscle group item only once.

For example, I want to create a new exercise, lets say Bench Press, what will be in the Chest muscle group. To be able to add the exercise, I click on a button, what takes me to a new window, and there will be all the muscle groups listed, I select Chest.

When I go to the new window, I query the database, and I want to list the items in a listview. However I have around 15 muscle groups and 270 exercises, the ideal outcome is to listeach muscle groups once, in order by name.

How do I do this? See attached picture. I kind of don't know how to set this up.

Thank you for your help in advance!

I've tried to query the collection, and to set up actions, but I can't add custom function or set the value properly.

I also have a custom fnction to filter the results after the query, I add the results to the button text but I'm getting errors.

import 'dart:convert';

import 'dart:math' as math;

import 'package:flutter/material.dart';

import 'package:google_fonts/google_fonts.dart';

import 'package:intl/intl.dart';

import 'package:timeago/timeago.dart' as timeago;

import '/flutter_flow/lat_lng.dart';

import '/flutter_flow/place.dart';

import '/flutter_flow/uploaded_file.dart';

import '/flutter_flow/custom_functions.dart';

import '/backend/backend.dart';

import 'package:cloud_firestore/cloud_firestore.dart';

import '/auth/firebase_auth/auth_util.dart';

String? getUniqueMuscleGroups() {

/// MODIFY CODE ONLY BELOW THIS LINE

List<String> getUniqueMuscleGroups(List<Map<String, dynamic>> documents) {

Set<String> muscleGroups = {};

for (var document in documents) {

if (document.containsKey('muscle_group')) {

muscleGroups.add(document['muscle_group']);

}

return muscleGroups.toList();

}

/// MODIFY CODE ONLY ABOVE THIS LINE

}

Query collection and filter the results by field items - only list field items once