Oppiskele Enums and Extensions for Flutter Code | Dart Language Core for Flutter

Enums in Dart are a powerful tool for representing a fixed set of related values, such as the possible states of a widget in Flutter. By using enums, you can make your code more readable and less error-prone, especially when handling things like loading, success, or error states in your UI.

main.dart


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import 'package:flutter/material.dart';

enum LoadState { loading, success, error }

class StatusWidget extends StatelessWidget {
  final LoadState state;

  const StatusWidget({Key? key, required this.state}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    switch (state) {
      case LoadState.loading:
        return const CircularProgressIndicator();
      case LoadState.success:
        return const Icon(Icons.check, color: Colors.green);
      case LoadState.error:
        return const Icon(Icons.error, color: Colors.red);
    }
  }
}

Dart extensions let you add custom methods or getters to existing types without modifying their original source code. This is especially useful for making your Flutter code cleaner and more expressive, such as by adding formatting helpers to strings or utility methods to collections.

main.dart


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extension DisplayFormat on String {
  String toTitleCase() {
    if (isEmpty) return this;
    return this[0].toUpperCase() + substring(1).toLowerCase();
  }
}

void main() {
  String name = "flutter";
  print(name.toTitleCase()); // Output: Flutter
}

Note

Using enums instead of strings for state management helps prevent typos, makes refactoring safer, and allows for better code completion in your IDE.

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main.dart


              123456789101112131415161718192021
            
import 'package:flutter/material.dart';

enum LoadState { loading, success, error }

class StatusWidget extends StatelessWidget {
  final LoadState state;

  const StatusWidget({Key? key, required this.state}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    switch (state) {
      case LoadState.loading:
        return const CircularProgressIndicator();
      case LoadState.success:
        return const Icon(Icons.check, color: Colors.green);
      case LoadState.error:
        return const Icon(Icons.error, color: Colors.red);
    }
  }
}

main.dart


              1234567891011
            
extension DisplayFormat on String {
  String toTitleCase() {
    if (isEmpty) return this;
    return this[0].toUpperCase() + substring(1).toLowerCase();
  }
}

void main() {
  String name = "flutter";
  print(name.toTitleCase()); // Output: Flutter
}

Note

Using enums instead of strings for state management helps prevent typos, makes refactoring safer, and allows for better code completion in your IDE.

Oliko kaikki selvää?

Kiitos palautteestasi!

Osio 1. Luku 5