How to use Data Handling in Flutter Using List.generate with Back4app

introduction in flutter, the simplest way for dynamic list creation is by using list generate it helps, especially when dealing with data fetched through a back end service like back4app whether it is dynamic ui elements, handling several entries of data, or optimization of network requests, list generate will at least ease your code and boost performance in this tutorial, we are going to see how to handle efficiently the backend data using list generate in flutter in this example, you will see how to create a simple flutter application with back4app to fetch and display user reviews dynamically, rating them in the process you will learn about processing backend data, network request optimization, and batch operations with list generate prerequisites to complete this tutorial, you will need a back4app account sign up for a free account at back4app com https //www back4app com a flutter development environment set up on your local machine follow the flutter installation guide https //flutter dev/docs/get started/install if you haven't set it up yet basic knowledge of dart, flutter widgets, and asynchronous programming step 1 – setting up your back4app backend create a back4app project log in to your back4app account https //dashboard back4app com/ and create a new project create a parse class in your back4app project, create a new parse class named review this class will store user reviews for different items (e g , products, movies, etc ) add the following fields username (string) the name of the user who submitted the review rating (number) the rating given by the user, typically a value between 1 and 5 comment (string) the review text or comment add sample data populate the review class with sample data to use in your flutter app get your back4app credentials navigate to your project settings to retrieve your application id and client key, which you’ll need to connect your flutter app to back4app step 2 – setting up your flutter project create a new flutter project open your terminal or command prompt and run add dependencies open pubspec yaml and add the following dependencies initialize parse in your app in lib/main dart , import the parse sdk and initialize it in the main function import 'package\ flutter/material dart'; import 'package\ parse server sdk flutter/parse server sdk flutter dart'; void main() async { widgetsflutterbinding ensureinitialized(); const keyapplicationid = 'your back4app app id'; const keyclientkey = 'your back4app client key'; const keyparseserverurl = 'https //parseapi back4app com'; await parse() initialize(keyapplicationid, keyparseserverurl, clientkey keyclientkey, autosendsessionid true); runapp(myapp()); } class myapp extends statelesswidget { @override widget build(buildcontext context) { return materialapp( home reviewscreen(), ); } } replace 'your back4app app id' and 'your back4app client key' with your actual back4app credentials step 3 – fetching and displaying data using list generate create the reviewscreen widget in lib/main dart , add a new widget that will fetch reviews from back4app and display them using list generate class reviewscreen extends statefulwidget { @override reviewscreenstate createstate() => reviewscreenstate(); } class reviewscreenstate extends state\<reviewscreen> { list\<parseobject>? reviews; @override void initstate() { super initstate(); fetchreviews(); } future\<void> fetchreviews() async { final query = querybuilder\<parseobject>(parseobject('review')); final response = await query query(); if (response success && response results != null) { setstate(() { reviews = response results as list\<parseobject>; }); } } @override widget build(buildcontext context) { return scaffold( appbar appbar(title text('user reviews')), body reviews == null ? center(child circularprogressindicator()) listview\ builder( itemcount reviews! length, itembuilder (context, index) { final review = reviews!\[index]; return reviewtile( username review\ get\<string>('username') ?? 'anonymous', rating review\ get\<int>('rating') ?? 0, comment review\ get\<string>('comment') ?? '', ); }, ), ); } } class reviewtile extends statelesswidget { final string username; final int rating; final string comment; reviewtile({required this username, required this rating, required this comment}); @override widget build(buildcontext context) { return card( margin edgeinsets symmetric(vertical 10, horizontal 15), child padding( padding const edgeinsets all(15 0), child column( crossaxisalignment crossaxisalignment start, children \[ text( username, style textstyle(fontweight fontweight bold), ), sizedbox(height 5), row( children list generate(5, (index) { return icon( index < rating ? icons star icons star border, color colors amber, ); }), ), sizedbox(height 10), text(comment), ], ), ), ); } } in this example, reviewtile is a custom widget that displays a user’s review the star rating is dynamically generated using list generate , creating a row of star icons based on the rating value retrieved from the backend step 4 – optimizing data fetching with list generate and future wait in cases where you need to fetch data from multiple backend endpoints simultaneously, you can use list generate in combination with future wait to optimize the process fetching multiple related records imagine you have another class named product and you want to fetch related reviews for multiple products at once you can use list generate to initiate these requests concurrently future\<void> fetchmultipleproductsreviews(list\<string> productids) async { list\<future\<list\<parseobject>>> requests = list generate(productids length, (index) { final query = querybuilder\<parseobject>(parseobject('review')) whereequalto('productid', productids\[index]); return query query() then((response) => response results as list\<parseobject>); }); list\<list\<parseobject>> allreviews = await future wait(requests); setstate(() { allproductreviews = allreviews; }); } this approach reduces the overall wait time by fetching data for all products simultaneously step 5 – performing batch operations using list generate if you need to perform batch updates or deletions on multiple records fetched from the backend, list generate can simplify the process batch update example here’s how you might update the status of multiple records in one go future\<void> updatemultiplereviews(list\<string> reviewids, string newstatus) async { list\<future\<parseobject>> updaterequests = list generate(reviewids length, (index) { parseobject review = parseobject('review') objectid = reviewids\[index]; review\ set('status', newstatus); return review\ save(); }); await future wait(updaterequests); print('all reviews updated'); } using list generate here allows you to efficiently perform operations on a large number of records in a single operation step 6 – testing and running your app run your app using flutter run you should see a list of user reviews, with each review showing a dynamically generated star rating using list generate if you implemented the batch operations and multi fetch example, test those scenarios as well to ensure everything works correctly conclusion in this tutorial, you learned how to use list generate in flutter to efficiently handle and display data retrieved from a backend, like back4app by using list generate , you can create dynamic ui elements, optimize data fetching, and perform batch operations in a clean and maintainable way this approach not only improves your app's performance but also keeps your codebase organized and easy to manage for more information on using back4app with flutter, check out the back4app flutter documentation https //www back4app com/docs/flutter/overview happy coding!