Navigating Environment Variables in Flutter Projects: Strategies for Effective Integration
Tags: flutter, dart, development, env
Published: 2024-01-07 15:32:47

In this blog post, we'll explore how to make your Flutter development environment more efficient by adjusting environment variables. There are two ways to do this. First, you can specify variables directly in the run command using `--dart-define=SOME_VAR=SOME_VALUE`. Alternatively, you can store them in a JSON file and then parse the file within your Flutter application.

## What are environment variables & why use them?
Environment variables are like secret codes for your computer, storing important information needed by different apps. They help control how programs run and behave. Imagine them as flexible tools that let you configure and customize your software without changing the code. Developers love them for securing things like API keys or database credentials, managing these details outside the code for better security and adaptability.

## How to get environment variables in Dart
In Dart, there are two ways to get environment variables. The first way is using `String.fromEnvironment` or `bool.fromEnvironment` functions (there are similar ones for `int` and `double`). The second, simpler method is using `Platform.environment`. Let's compare them:

**String.fromEnvironment**
- **Purpose:** Access environment variables defined during compilation or running using `--dart-define` flags.
- **Scope:** Dart code only.
- **Usage:**
  ```dart
  const apiUrl = String.fromEnvironment('API_URL', defaultValue: 'http://localhost:8080');
  ```

**Platform.environment**
- **Purpose:** Access platform-specific environment variables.
- **Scope:** Dart code and platform channels.
- **Usage:**
  ```dart
  String sdkVersion = Platform.environment['FLUTTER_SDK_VERSION'];
  ```
**Key Differences:**
- **Source:**
  - **String.fromEnvironment:** `--dart-define` flags during compilation or running.
  - **Platform.environment:** Platform-specific variables.

- **Visibility:**
  - **String.fromEnvironment:** Dart code only.
  - **Platform.environment:** Dart code and platform channels.

- **Mutability:**
  - **String.fromEnvironment:** Constant (set at compile time).
  - **Platform.environment:** Dynamic (changeable at runtime).

**When to Use Each:**
- Use **String.fromEnvironment** for:
  - Sensitive information.
  - Values changing based on build configurations.
- Use **Platform.environment** for:
  - Platform-specific settings.
  - Communicating with native code.

**Best Practices:**
- Keep sensitive info in environment variables using `--dart-define` flags.
- Don't hardcode sensitive values.
- Use a separate config file for env variables in production.
- Consider a dependency injection framework for managing env variables in larger projects.

### Setting environment variables through the run command:

Enhancing your Flutter development environment can be as easy as tweaking the run command. By adding `--dart-define=SOME_VAR=SOME_VALUE`, you're telling Flutter to use specific values during execution. For example:

```bash
flutter run --dart-define=API_KEY=your_actual_api_key
```

This method lets you customize environment variables on the fly, making your development process more efficient.

### Simplifying with a JSON file:

For a more organized approach, create a JSON file (let's call it `env.json`) to store your variables:

```json
{
   "SOME_VAR": "SOME_VALUE",
   "SOME_VAR_2": "SOME_VALUE_2"
}
```

Now, when running Flutter, use the `--dart-define-from-file` flag to parse variables from this JSON:

```bash
flutter run --dart-define-from-file=env.json
```

This method is great for managing multiple variables, enhancing the organization and readability of your configuration. It's a win for a smoother development environment in Flutter.

#### VS Code
To incorporate custom Flutter commands like `--dart-define` and define the path for an environment file in Visual Studio Code, follow these steps:

1. Open the launch.json file by clicking on the "Run and Debug" button, then selecting the settings icon.

![Setting icon](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/ppxrvule8htw3vnp8b1a.png)
2. Inside the launch.json file, locate the configurations section.

3. Add the desired args, such as `--dart-define=BASE_URL=http://localhost:3000`, within the configuration you want. For instance:

   ```json
   {
       "name": "testapp",
       "request": "launch",
       "type": "dart",
       "args": [
           "--dart-define=BASE_URL=http://localhost:3000"
       ],
       "env": {
           "VAR_EXAMPLE": "VALUE"
       }
   }
   ```

   Ensure the values match your project structure.

This allows you to customize your Flutter project settings directly within Visual Studio Code, enhancing your development experience.

As you can observe, we've included an "env" key. This is a feature introduced by Visual Studio Code to facilitate the management of your environment variables.

### Conclusion
In conclusion, optimizing your Flutter development environment through environment variable adjustments, be it in run commands or a JSON file, offers efficiency and flexibility. Recognizing their significance for securing sensitive data and adapting to various configurations is crucial. Dart's tools like `String.fromEnvironment` and `Platform.environment` provide dynamic control, while Visual Studio Code simplifies integration through its launch.json file. This streamlines the process, enhancing the security and efficiency of Flutter applications. Choosing the method that aligns with your project's needs contributes to a more seamless and productive development experience.