Arduino Starter Kit error (11th project) 'prevSwitchState' was not declared in this scope

Using Arduino Project Guidance
1

I have made it to the 11th project of the starter kit.
When i compiled the code, it gave me an error:

'prevSwitchState' was not declared in this scope

I don't know what's wrong. I typed everything out of the projects book, but it didn't show how to make the previous switch state variable.
Can you help me?
Here's the code if you need it:

#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
const int switchPin = 6;
int switchState = 0;
int reply;
void setup() {
  lcd.begin(16, 2);
  pinMode(switchPin, INPUT);
  lcd.print ("Ask the");
  lcd.setCursor(0, 1);
  lcd.print("Crystal Ball!");
}
void loop() {
  switchState =digitalRead(switchPin);
  if (switchState != prevSwitchState)
    if (switchState == LOW) {
      reply = random(8);
      lcd.clear();
      lcd.setCursor(0, 1);
      switch(reply){
        case 0:
        lcd.print("Yes");
        break;
        case 1:
        lcd.print("Most likely");
         break;
        case 2:
        lcd.print("Certainly");
         break;
        case 3:
        lcd.print("Outlook good");
         break;
        case 4:
        lcd.print("Unsure");
         break;
        case 5:
        lcd.print("Ask again");
         break;
        case 6:
        lcd.print("Doubtful");
         break;
        case 7:
        lcd.print("No");
        break;
      }
    }
}

Here's the error:

C:\Users\vados\AppData\Local\Arduino15\RemoteSketchbook\ArduinoCloud\58373ecb-0049-4b7c-87cc-64c1599e2523\Crystal_Ball\Crystal_Ball.ino: In function 'void loop()':
C:\Users\vados\AppData\Local\Arduino15\RemoteSketchbook\ArduinoCloud\58373ecb-0049-4b7c-87cc-64c1599e2523\Crystal_Ball\Crystal_Ball.ino:15:22: error: 'prevSwitchState' was not declared in this scope
   if (switchState != prevSwitchState)
                      ^~~~~~~~~~~~~~~
C:\Users\vados\AppData\Local\Arduino15\RemoteSketchbook\ArduinoCloud\58373ecb-0049-4b7c-87cc-64c1599e2523\Crystal_Ball\Crystal_Ball.ino:15:22: note: suggested alternative: 'switchState'
   if (switchState != prevSwitchState)
                      ^~~~~~~~~~~~~~~
                      switchState

exit status 1

Compilation error: 'prevSwitchState' was not declared in this scope
2

I think you missed a line. But I don't have the book.

You can add int prevSwitchState = 1; after int switchState = 0;.

3

Welcome to the forum

Change

int switchState = 0;

to

int switchState = 0;
int prevSwitchState = 0;
4

That piece of code worked, but apparently i didn't declare "switchState".

5

The error referred to prevSwitchState, not to switchState.

By the way, thanks for using code tags in your first post, for the code as well as the errors.

6

The sketches for the Starter Kit are all available in the IDE examples and #11 includes these lines

// variable to hold the value of the switch pin
int switchState = 0;

// variable to hold previous value of the switch pin
int prevSwitchState = 0;
7

@sashaparadox Welcome to the forum.

Unlike many(most) first time posters, you have made a perfect post using code tags and posting the complete error message. Well done.

As @UKHeliBob says, the Starter Kit codes are available in the IDE with
File>Examples>10.StarterKit_BasicKit and there is no need to type the example codes into the IDE.