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Celest is the Flutter cloud platform. We enable Flutter and Dart developers to declaratively define their backend infrastructure in Dart.

And to stay up-to-date on the future of Celest, including managed deployments, join our waitlist at celest.dev.

To use Celest in your Flutter app, you need the following prerequisites:

1. Install Flutter
2. Create a new Flutter project (or choose an existing one)
3. Download and install the Celest CLI

That’s it! You are now ready to start building your backend - all in Dart!

Start by first creating a new Flutter project. If you have an existing Flutter project, you can use that instead. To start a new Flutter project, go to your console and run the following command.

$ flutter create <flutter_app>

Then, navigate to your new Flutter app directory.

$ cd <flutter_app>

Once you are in your Flutter app directory, run the following command to initialize your Celest project.

$ celest start

Once the command executes, Celest will spin up a local environment and watch for changes made to your backend, generating a Dart client for you to test your changes.

The CLI will also create a folder in your project called celest, which will include the following files.

flutter_app/
└── celest/
    ├── functions/                        # Celest Functions folder
    |   └── greeting.dart                 # Example API file
    ├── lib/
    │   │── client.dart                   # Generated client for your Flutter app
    │   ├── models/                       # Custom API models
    |   |   └── person.dart
    │   └── exceptions/                   # Custom API exceptions
    |       └── bad_name_exception.dart
    └── test/                             # Tests for your backend

To get started building your serverless cloud function, navigate to the <flutter_app>/celest/functions/ folder and create a file named <api_name>.dart. You can create as many APIs as you want in this directory. Think of each file as a way to organize and group multiple Celest Functions of similar functionality into a namespace.

Celest Functions are defined as top-level functions as shown below.

Future<String> sayHello({
  required String name,
}) async {
  return 'Hello, $name';
}

Future<String> sayGoodbye({
  required String name,
}) async {
  return 'Goodbye, $name';
}

That's all you need to define your API! Now, you can connect your Flutter app to your cloud functions by using the code-generated client as shown in the following example. Replace the contents of the main.dart file in your Flutter app to the following code-snippet.

import 'package:flutter/material.dart';
// Import the generated Celest client
import 'package:celest_backend/client.dart';

void main() {
  // Initializes Celest in your Flutter app
  celest.init();
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Homepage'),
        ),
        body: Center(
          child: FutureBuilder(
            // Call your function using the Celest client
            future: celest.functions.greeting.sayHello(name: 'Celest'),
            builder: (_, snapshot) => switch (snapshot) {
              AsyncSnapshot(:final data?) => Text(data),
              AsyncSnapshot(:final error?) =>
                Text('${error.runtimeType}: $error'),
              _ => const CircularProgressIndicator(),
            },
          ),
        ),
      ),
    );
  }
}

You have now set up your Celest project and integrated it into your Flutter app. Follow our documentation to learn more about using Celest Functions.

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