Smart switches have been installed to monitor and automate name devices - NSC Information Technology - Question 3 - 2023 - Paper 1

The energyUsed method calculates the energy used based on the number of hours the device is on:

function TSmartSwitch.energyUsed(hours: Integer): Double;
begin
  Result := fPowerUsage * hours / 1000; // Converting to kWh
end;

To implement the setSwitchStatus method, use the following code:

procedure TSmartSwitch.setSwitchStatus(status: Boolean);
begin
  fSwitchStatus := status;
end;

To create the toString method for the TSmartSwitch class:

function TSmartSwitch.toString: String;
begin
  Result := Format('Switch ID: %d
Device: %s
Power usage: %.2f W
Switch status: %s',
                 [fSwitchID, fDevice, fPowerUsage, determineSwitchStatus()]);
end;

To instantiate the object from the combo box:

var
  iSwitchID: Integer;
  sDevice: String;
  iPowerUsage: Integer;
begin
  iSwitchID := cmbQ3_2.ItemIndex;
  sDevice := lstQ3_2.Items[iSwitchID];
  // Extract power usage from sDevice
  // ... (code to extract)
  objSmartSwitch := TSmartSwitch.Create(iSwitchID, sDevice, iPowerUsage);
  // Display objSmartSwitch.toString in rcdQ3_2
end;

To set the switch status based on the radio group:

if rgrpQ3_2.ItemIndex = 0 then
  objSmartSwitch.setSwitchStatus(True)
else
  objSmartSwitch.setSwitchStatus(False);

// Display results
rcdQ3_2.Lines.Add(IntToStr(objSmartSwitch.getSwitchID) + ' - Status: ' + objSmartSwitch.determineSwitchStatus());

To implement the writing to the file:

var
  logFile: TextFile;
begin
  AssignFile(logFile, 'log.txt');
  Append(logFile);
  WriteLn(logFile, Format('%s, %s, Switch ID: %d, Status: %s', [DateToStr(Date), TimeToStr(Time), objSmartSwitch.getSwitchID, objSmartSwitch.determineSwitchStatus()]));
  CloseFile(logFile);
end;

To calculate power usage when the user inputs the number of hours:

var
  hours: Integer;
begin
  hours := StrToInt(edtQ3_2.Text);
  ShowMessage('Energy used: ' + FloatToStr(objSmartSwitch.energyUsed(hours)) + ' kWh');
end;