what is newValue in swift? and why it cant be changed

Question

why i cant change newValue when its not initialized anywhere

class Temperature {
var celsius: Float = 0.0
var fahrenheit: Float {
get {
return ((celsius * 1.8) + 32.0)
}
set {
celsius = (newValue - 32)/1.8
}
}
}

let temp = Temperature()
temp.fahrenheit = 99
print (temp.celsius)

Answer 1

`fahrenheit` is a property member of `Temperature` class, it supports getter and setter.

The getter returns the calculation result of `celcius` value to `fahrenheit`.

The setter adjusts `celcius` value based on given `newValue` (expected to be a value in fahrenheit)

There is no need to change `newValue` because it was an input rather than output.

For the example snippet shown in Description, `newValue` stores the property value assigned at second to last line (temp.fahrenheit = 99)

(Edited)