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Flutter Fastlane: Your Ally in Streamlining App Deployment Workflows

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Nidhi Sorathiya

September 4, 2023

Nidhi Sorathiya

September 4, 2023

The world of mobile app development has evolved at a lightning-fast pace, and with this rapid growth, complexity in the build and deployment process has increased. One of the key tools embraced by developers worldwide to streamline app deployments is Fastlane. In this article, we will explore the seamless nexus of Flutter Fastlane.

Releasing an app is typically a tangle of tasks, involving code compilation, testing, incrementing the build number, code signing, and finally, app distribution. Fastlane integrates these various stages and automates them to offer a smoother development process. From handling secrets to deploying on the Google Play Store or Apple App Store, Fastlane takes on most of the heavy lifting.

In this article, you will cross paths with running tests, deploying your Flutter application to app stores, and even setting it up for continuous integration (CI) pipelines with Fastlane. The essential tools we'll explore are Firebase App Distribution and the App Store, among others.

What is Fastlane?

Fastlane is an open-source tool suite that is designed to automate beta deployments and releases for your app. It was built to simplify the configuration and automation of tasks in your mobile app development environment. This allows developers to focus on what matters most: creating stunning apps. Fastlane handles the tedious tasks involved in deploying a new release and turns it into an effortless process.

Whether you design iOS apps or Android applications, Fastlane has got your back. You can automate just about any task: running the Flutter test command or deploying your app for user testing with Firebase App Distribution or to the Google Play store.

Fastlane for Flutter

Fastlane is a versatile tool, perfect to integrate with Flutter. It makes the handling of multiple tasks during the app's development process a breeze. Flutter fastlane integration can significantly simplify your release workflow, especially while releasing beta builds, distributing apps, and coping with erratic app store review times.

In the upcoming sections, we will take a deep dive into setting up Fastlane for a Flutter project. Our focus will be on understanding its advantages in deploying a Flutter app and how it significantly reduces the manual work involved in the app release cycle.

Setting Up Your Environment

Setting up the local environment correctly is a foundational step to ensure a smooth and effective fastlane setup. Ensuring that the build and deployment process is working locally is crucial before moving to a cloud system such as CI/CD service. You can also opt for continuous delivery from the local machine.

Local setup for Fastlane with Flutter

To kick things off, let's learn how to install Fastlane on your local machine. You can do it in one of two ways. Either you can install fastlane gem using:

Or prefer to install it using the brew command as:

For further details, you can visit the Fastlane installation guide.

Once you have installed Fastlane, the next step is to set up an environment variable, named FLUTTER_ROOT. This variable should be set to the root directory of your Flutter SDK. Remember, this is a crucial step, especially when you want to deploy scripts for iOS.

Integrating Fastlane with Your Flutter Project

Now, create your Flutter project as you normally would and ensure that your project builds successfully via the flutter build appbundle for Android and flutter build ipa for iOS. After verifying this, you can proceed with the initialization of the Fastlane projects for Android and iOS separately.

In your Android directory of your project, run the following command:

Similarly, in your iOS directory, initialize Fastlane in the same way. This forms the basic fastlane setup for your Flutter project and gets you geared up for the next steps of the process.

Integrating Fastlane with Your Flutter Project

Once you've accomplished the local setup, the next phase involves integrating Fastlane more deeply into your Flutter project.

Setting Up the Appfiles

The heart of your Fastlane configuration resides in the Appfiles. Ensuring that they have ample metadata for your app is essential for successful deployment. The location of these files in your Flutter project depends on the target operating system.

In Android, you need to verify the package_name in [project]/android/fastlane/Appfile matches the package name in AndroidManifest.xml.

In the case of iOS, you need to check that app_identifier in [project]/ios/fastlane/Appfile matches the bundle identifier in Info.plist. Fill the fields like apple_id, itc_team_id, and team_id with your respective account information.

Registering Local Login Credentials for Stores

It's crucial to set up the local login credentials for the respective app stores.

For Android, follow the Supply setup steps. Verify that the fastlane supply init succeeds in syncing data from your Play Store console. Remember to treat the .json file, which contains key account information, like your password. Do not check it into any public source control repositories.

For iOS, you already entered your iTunes Connect username in your Appfile’s apple_id field during the setup. Set the FASTLANE_PASSWORD shell environment variable with your iTunes Connect password to circumvent being prompted for credentials while uploading to iTunes/TestFlight.

Setting Up Code Signing

Code signing is a crucial step to ensure the software's integrity and authenticity. It's proof that the app comes from a known source and hasn't been tampered with.

For Android: Follow the Android app signing steps.

For iOS: Sign using a distribution certificate instead of a development certificate when you want to test and deploy using TestFlight or the App Store. Create and download a distribution certificate from the Apple Developer Account console. Open your project's workspace, [project]/ios/Runner.xcworkspace/, and select the distribution certificate in your target settings pane.

By now, you have integrated Fastlane fully into your Flutter project. In the upcoming section, we'll look at how to automate the release process using Fastlane.

Automating Release Process Using Fastlane

This stage of integration involves the creation of a Fastfile script for each platform and the variety of tasks it automates in the release process.

Setting Up The Fastfile Script

In Android, following the fastlane Android beta deployment guide could be as simple as adding a lane that calls upload_to_play_store. We will be making use of the app bundle that Flutter build already built, and you can set the aab argument to ../build/app/outputs/bundle/release/app-release.aab.

For iOS, you can follow the Fastlane iOS beta deployment guide. To avoid rebuilding the project, you can specify the archive path in the Fastfile script as follows,

Running the Deployment Locally

After Fastfile configuration, you can perform deployments locally. Build the release mode app using Flutter build appbundle for Android or Flutter build ipa for iOS. To execute the Fastfile script, head over to each platform directory (android or ios) and run bundle exec fastlane [name of the lane you created]. For instance, if "deployment" is the name of your lane, follow these steps:

For Android:

For iOS:

Once you've tested deploying your app to the respective stores, you’re ready to move the deployment process to a continuous integration (CI) system or a cloud system.

Integrating Fastlane with CI/CD Workflows

Fastlane becomes even more powerful when used in combination with continuous integration (CI) systems like Travis, GitHub Actions, or CircleCI. As Fastlane handles all the app-building tasks, including running tests and deploying to Google Play or the App Store, using CI systems can ensure all changes are tested and deployment-ready, even before they are merged.

Cloud Build And Deploy Setup

Before integrating with a CI/CD service, it's crucial to ensure the process works efficiently in the local setup. The focus here is on handling your environment variables and website credentials to be secure in an ephemeral and untrusted environment, like most CI systems.

Handling Private Data and Environment Variables

CI systems generally support encrypted environment variables to store private data. While the Flutter app is being built, these environment variables can be passed using the --dart-define MY_VAR=MY_VALUE argument. Any console interactions in pull requests should be handled carefully to avoid revealing these secrets accidentally.

Making Login Credentials Ephemeral

The goal is to avoid leaving your credentials and certificates on the CI server:

For Android:

  • Remove the json_key_file field from the Appfile and store the string content of the JSON in your CI system’s encrypted variable. Read the environment variable directly in your Fastfile.
  • Serialize your upload key (for example, using base64) and save it as an encrypted environment variable.

For iOS: Switch your local environment variable FASTLANE_PASSWORD to use encrypted environment variables on your CI system. You'll need to synchronize your certificates across machines using fastlane’s Match system.

Configuring Fastlane for CI/CD

With the keys and certificates set, it's recommended to use a Gemfile to make sure the Fastlane dependencies between local and CI systems are identical. Create a Gemfile and run the bundle update. Check both Gemfile and Gemfile.lock into source control. Use bundle exec fastlane instead of Fastlane when running locally.

Incorporate Fastlane into the CI script in your repository root, such as .travis.yml or .cirrus.yml. Consult the Fastlane CI documentation for specific setup instructions.

Fastlane's versatility and powerful integrations make it a must-have for any developer aiming for a smooth and efficient deployment workflow. No wonder it's frequently the tool of choice when building and deploying Flutter applications to the app stores.

Case Study: Implementing Fastlane in Major CI Systems

After exploring the benefits of Fastlane for automating tedious tasks such as running tests and deploying to the App Store or Google Play, it's fitting to look at some practical implementations of Fastlane.

Implementation in GitHub Actions

GitHub Actions, an automation software that allows you to build end-to-end continuous integration (CI) and continuous delivery (CD) capabilities directly in your repository, can work exceptionally well with Fastlane. Together with GitHub Actions, Fastlane can automate your release process, run your test suite on every pull request, and create new app store versions right from your repository.

Implementation in Cirrus

Cirrus CI, a powerful and flexible CI service famous for its container-agnostic and task-oriented approach can also be an excellent platform to incorporate Fastlane. Controls over computing resources shared and dependent tasks, and matrix modifications, among other advanced features, mesh well with Fastlane.

Implementation in Travis

Travis CI, trusted by thousands for its simple setup process and seamless integration with GitHub, is another solid choice for implementing Fastlane. The structure of a .travis.yml configuration file for pulling the repository, installing and setting up Fastlane, and running the lanes is intuitive and uncomplicated to write.

With these case studies, you should have a clear idea of how to utilize Fastlane in different popular CI systems. Harnessing Fastlane in conjunction with these platforms can be the key to a fully automated and efficient CI/CD pipeline for your Flutter apps.

Accelerate Your App Deployment With Flutter Fastlane!

Through the course of this blog, I've provided a comprehensive guide on how to manage your Flutter applications more efficiently using Fastlane. We've discussed the advantages of integrating Fastlane with the Flutter framework and how it can streamline the app's development process, especially when releasing beta builds, distributing apps, and handling app store review times.

Fastlane truly shines by automating tedious tasks, offering tools such as Firebase App Distribution and the new App Store, thereby simplifying the complexities of the process.

However, nothing is without its trade-offs. Although Fastlane significantly reduces human effort, it does come with a steep learning curve. Adjusting and refining the Fastlane workflows might take time and perseverance. Debugging Fastlane errors could be challenging for someone new to Ruby or the distinctive debugging output that Fastlane provides. When appropriately implemented with your existing CI/CD workflows, it can significantly accelerate your app deployment, making the development process a breeze.

Reference & Further Readings

For those who want to dig in deeper and learn more, there are numerous resources available online. Fastlane docs and Fastlane's official documentation for Flutter written by the Flutter team are an excellent place to start!

I hope you found this blog post enjoyable and learned something about effortless app deployments with Flutter Fastlane. Keep deploying amazing apps! 🚀

Frequently asked questions

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