What Dart is
Dart is a statically typed language with familiar syntax. A developer who has written Java, JavaScript, C#, or Kotlin can usually read Dart code without preparation and start writing it fairly quickly.
The language has two modes. During development, code runs in a way that lets you see changes almost instantly, without rebuilding the app. For release, the same code compiles to native machine code for phones and computers or to JavaScript for the browser. So Dart combines a convenient development workflow with fast performance in the finished app.
Where Dart is used
- Flutter mobile apps. The main and most common use case.
- Flutter web and desktop apps. Internal dashboards, employee tools, and apps for Windows, macOS, and Linux.
- Utilities and scripts. Code generation, file processing, helper tools for the development team.
- Backend. Technically possible but rare: there are far fewer ready-made libraries and specialists here than for other languages.
Advantages of Dart
- Null safety. The language requires you to declare explicitly where data may be missing and checks this before the code runs. This eliminates a whole class of app crashes.
- Easy async programming. Server requests, file reads, and other long-running operations read almost like ordinary sequential code, with no nested callbacks.
- Isolates for heavy computation. Processing large volumes of data can be moved to a separate thread of execution so the UI doesn't freeze.
- Built-in tooling. A code analyzer, automatic formatting, testing, and a package manager come standard and are configured the same way in every project.
Limitations of the language
- Tightly tied to Flutter. Dart sees little use outside Flutter, so choosing the language effectively means choosing Flutter.
- Fewer specialists. There are fewer Dart developers than JavaScript or Kotlin developers. It's important that the code is clear and documented, so handing the project to another team is easier.
- A small ecosystem outside mobile. For backend, data analytics, or machine learning, other languages offer a much wider range of ready-made solutions.
- Uneven package quality. Some packages are maintained by individual enthusiasts. Every dependency should be evaluated before it's added to a project.
When another language is a better choice
We don't recommend Dart for its own sake. Another language makes more sense if:
- your team already writes TypeScript and React. Then React Native is the more logical choice for a mobile app, since you can reuse your skills and part of the code;
- you only need a backend or data processing. Languages with a mature server-side ecosystem are better for that;
- the app will be Android-only and deeply integrated with the system. Then Kotlin is the more natural choice.
Migrating to sound null safety
In early versions of Dart, any variable could turn out to be null, and the resulting errors showed up in front of users. The language later added sound null safety, and in newer versions it became mandatory.
For older projects, this means they won't build with current Flutter versions without a migration. We migrate gradually, package by package: first we update dependencies, then we convert your own code and check every place where a value can genuinely be missing. A mechanical fix "just to make it build" only hides bugs, so we handle each case individually.
How we clean up Dart code
In Flutter projects that have grown for a long time without rules, logic often lives directly in the screens. We gradually split the code into layers:
- UI: only displays data and passes user actions along;
- logic: rules, calculations, and validations that can be tested without a phone;
- data: server calls, cache, local database, sync.
This separation lets you change the design without touching calculations and move to a new backend without rewriting screens. Shared parts needed by several of the company's apps are packaged as separate internal packages.
Tests for app logic
Once logic is separated from screens, it can be tested automatically, without a phone and without manually walking through scenarios. Dart tests run in seconds and show whether a new change broke a discount calculation, form validation, or server response handling.
We don't aim to cover every line with tests. We focus first on what costs money or user trust: payments, calculations, authentication, data storage. For these parts, tests pay for themselves within the first few updates.
New code or improving existing code
In a new project, we enable strict analyzer rules, automatic formatting, and tests for key scenarios from day one. That's cheaper than cleaning things up later.
In an existing project, we don't rewrite everything at once. First we fix what blocks updates and releases, then we gradually untangle the most problematic modules alongside new feature development. The app keeps running and receiving updates the whole time.
What affects cost
- Code size: the number of screens, modules, and custom packages.
- Project age: how far behind the Dart, Flutter, and dependency versions are.
- Test coverage: without tests, every change takes longer to verify manually.
- Depth of changes: targeted fixes, migration, or architectural rework.
After an audit, you get a prioritized list of issues and a phased work plan.
Frequently asked questions
Is it worth learning Dart if we already write JavaScript? The syntax is familiar, so the switch is usually easy. But if you're not planning to use Flutter, there's little point.
Our app won't build with the latest Flutter. What should we do? The usual cause is outdated packages and a missing null safety migration. We'll start with an audit and show you how much work is needed.
Can you write a backend in Dart? You can, but for most projects we'll recommend a language with a broader server-side ecosystem and keep Dart for the app.
Will you take over a Dart project from another team? Yes. First we get familiar with the code and dependencies, then we support and evolve the app on an ongoing basis.
Why Promodex
Since 2015, Promodex has completed 750+ projects in development, design, and marketing. Our own in-house developers work on the code, with no subcontractors. We don't promise to rewrite everything from scratch: first we explain the state of your project, which changes will deliver the most value, and why. Terms are transparent, so you know what's being done and why, and after the work is complete we stay on hand for support and further development.
