antklim

class OperandInput extends StatefulWidget {
  final String label;
  final num initValue;
  final num memory;
  final ValueChanged<String> onChanged;

  const OperandInput(
      {Key key, this.label, this.initValue, this.memory, this.onChanged})
      : super(key: key);

antklim

class CalculusScreen extends StatefulWidget {
  @override
  _CalculusScreenState createState() => _CalculusScreenState();
}

class _CalculusScreenState extends State<CalculusScreen> {
  num memory;
  num calculatorResult; // current operation result

  void onMemorise() {

antklim

class _CalculusScreenState extends State<CalculusScreen> {
  ...
    
  void onCalulatorResultChanged(num value) {
    setState(() {
      calculatorValue = value;
    });
  }

  @override

antklim

class _CalculatorInputState extends State<CalculatorInput> {
  ...
  num get calculatorValue {
    switch (operation) {
      case Operation.addition:
        return operandA + operandB;
      case Operation.subtraction:
        return operandA - operandB;
      case Operation.multiplication:
        return operandA * operandB;

antklim

class _CalculatorInputState extends State<CalculatorInput> {
  final operations = <Operation, String>{
    Operation.addition: 'Addition',
    ...
  };

  Operation operation = Operation.addition;
  num operandA = 0;
  num operandB = 0;

antklim

enum Operation { addition, subtraction, division, multiplication, sqrt }
enum Operand { A, B }

class CalculatorUseCase {
  num memory;
  Operation operation;
  num operandA;
  num operandB;

  CalculatorUseCase(

antklim

void main() {
  group('Calculator use case', () {
    group('calculates value of', () {
      Map<CalculatorUseCase, num> testCases = {
        CalculatorUseCase(operation: Operation.addition, operandA: 1, operandB: 2): 3,
        ...
      };
      testCases.forEach((useCase, expected) {
        test('${useCase.operation}', () {
          expect(useCase.value, expected);

antklim

class _CalculusScreenState extends State<CalculusScreen> {
  CalculatorUseCase useCase = CalculatorUseCase();

  void onMemorise() {
    setState(() {
      useCase.memorise();
    });
  }

  void onResetMemory() {

antklim

class CalculatorInput extends StatefulWidget {
  final CalculatorUseCase useCase;

  const CalculatorInput({Key key, this.useCase}) : super(key: key);

  @override
  _CalculatorInputState createState() => _CalculatorInputState();
}

class _CalculatorInputState extends State<CalculatorInput> {

antklim

class OperandInput extends StatefulWidget {
  final String label;
  final Operand operand;
  final CalculatorUseCase useCase;
  final Function onChanged;

  const OperandInput({Key key, this.label, this.operand, this.useCase, this.onChanged}) : super(key: key);

  @override
  _OperandInputState createState() => _OperandInputState();