Blynk Switch

Excuse me , Sir
i want to get number value from a switch of blynk to my device (nodeMCU)
I mean , I want that when I will turn ON or OFF the switch of Blynk , It will send a value to the device.
So, what should i write in the code ?

By using the Blynk virtual button from the app it sends 1 or 0 according to the state of the button(IN THE BLYNK APP).

In the code you need to read the value by

BLYNK_WRITE(V1) {
  int switchstate = param.asInt();
  if (switchstate == 1) {
    // DO SOMETHING
  } if (switchstate == 0) {
    //DO SOMETHING ELSE
  }
}

Hope this is what you are looking for. If not tell us more on what you are working on and the end point.