Project: Temperature Converter in Dart

Introduction

The Temperature Converter converts between Celsius, Fahrenheit, and Kelvin. It demonstrates enum usage, switch expressions, static methods, and input validation in a practical context.

Conversion Formulas

Full Code

enum TempUnit { celsius, fahrenheit, kelvin }

class TemperatureConverter {
  static double toCelsius(double value, TempUnit from) {
    return switch (from) {
      TempUnit.celsius    => value,
      TempUnit.fahrenheit => (value - 32) * 5 / 9,
      TempUnit.kelvin     => value - 273.15,
    };
  }

  static double fromCelsius(double celsius, TempUnit to) {
    return switch (to) {
      TempUnit.celsius    => celsius,
      TempUnit.fahrenheit => celsius * 9 / 5 + 32,
      TempUnit.kelvin     => celsius + 273.15,
    };
  }

  static double convert(double value, TempUnit from, TempUnit to) {
    if (from == TempUnit.kelvin && value < 0) {
      throw ArgumentError('Kelvin cannot be negative');
    }
    return fromCelsius(toCelsius(value, from), to);
  }

  static String symbol(TempUnit unit) => switch (unit) {
    TempUnit.celsius    => '°C',
    TempUnit.fahrenheit => '°F',
    TempUnit.kelvin     => 'K',
  };
}

void main() {
  void show(double v, TempUnit from, TempUnit to) {
    try {
      var r = TemperatureConverter.convert(v, from, to);
      print('$v$${TemperatureConverter.symbol(from)} = $${r.toStringAsFixed(2)}$${TemperatureConverter.symbol(to)}');
    } on ArgumentError catch (e) { print('Error: $${e.message}'); }
  }

  show(100,  TempUnit.celsius,    TempUnit.fahrenheit); // 100°C = 212.00°F
  show(32,   TempUnit.fahrenheit, TempUnit.celsius);    // 32°F = 0.00°C
  show(300,  TempUnit.kelvin,     TempUnit.celsius);    // 300K = 26.85°C
  show(-10,  TempUnit.kelvin,     TempUnit.fahrenheit); // Error
}

100.0°C = 212.00°F
32.0°F = 0.00°C
300.0K = 26.85°C
Error: Kelvin cannot be negative

🧠 Quiz

Summary

The temperature converter uses enums for type-safe units and a two-step conversion (via Celsius) to handle all unit pairs with only two switch expressions. Input validation in the convert method catches physically impossible Kelvin values.