What Are Extensions?

Dart extensions allow the addition of methods and properties to any type, including built-in types from the Dart SDK or third-party libraries, without the need for subclassing. This capability is invaluable for enhancing classes with extra functionality seamlessly, leading to more concise, readable, and expressive code.

Making Code Cleaner and More Readable

A key benefit of using extensions is the ability to create cleaner and more intelligible code. Let’s look at a basic example involving a double extension.

Suppose you want to display a double value in a text widget as currency. Instead of appending the currency symbol repeatedly, you can define an extension.

extension DoubleExtension on double {

String get inr => "$this ₹";

String get usd => "$this $";

}

Now, you can use this extension in your text widgets as follows:

Text(100.00.inr) // INR

Text(100.00.usd) // USD

Notice how much more streamlined and maintainable the code has become—this illustrates the power of Dart extensions.

Theme and Color Extensions

Prior to using extensions, accessing theme data or color schemes involved repetitive method calls:

final theme = Theme.of(context);

final primaryColor = theme.colorScheme.primary;

Using extensions simplifies this:

extension ThemeExtension on BuildContext {

ThemeData get theme => Theme.of(this);

}

extension ColorExtension on BuildContext {

ColorScheme get colorScheme => Theme.of(this).colorScheme;

Color get primary => colorScheme.primary;

}

You can then access properties directly, resulting in cleaner code:

final theme = context.theme;

final primaryColor = context.primary;

Navigation and Dialog Extensions

Previously, showing dialogs and snack bars required boilerplate code. However, with extensions, this can be reduced significantly.

extension NavigationExtension on BuildContext {

Future showMyDialog({required Widget child, bool isDismissible = true}) {

return showDialog(context: this, builder: (context) => child, barrierDismissible: isDismissible);

}

void showSuccessSnackBar(Widget child, {bool? isDismissible, Duration? duration}) {

ScaffoldMessenger.of(this)

..clearSnackBars()

..showSnackBar(SnackBar(

content: child,

backgroundColor: Colors.green,

dismissDirection: isDismissible ?? true ? DismissDirection.down : DismissDirection.none,

duration: duration ?? const Duration(seconds: 4),

));

}

}

Now, displaying a dialog or a success snack bar is much more concise:

context.showMyDialog(child: MyCustomDialog());

context.showSuccessSnackBar(Text('Operation successful!'));

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TextStyle Extensions

Before extensions, working with text styles could lead to verbose code. With extensions, you can streamline this:

extension TextStyleHelper on BuildContext {

TextStyle? get bodyMedium => Theme.of(this).textTheme.bodyMedium;

}

Now, applying styles becomes more readable:

Text("100.00", style: context.bodyMedium!.onPrimary(context).bold);