Cannot get and set value using completion block in Xcode 10.1 - swift

Question

I'm using Xcode 10.1 where I tried to calculate the radius in a completion block by setting the value of another variable called as diameter. The code is given below
import UIKit
import Foundation
var radius:Double = 10
var diameter: Double{
get{
return radius * 2
}
set{
radius = newValue
}
}
diameter = 30
print(diameter)
I'm expecting that the output should be 60.0 but it showing:
error: Computed property.playground:43:1: error: variables currently
must have an initial value when entered at the top level of the REPL
var area: Double{
The output is properly shown in the online compiler of swift but not in Xcode. Now How to get the proper output?

Answer 1

You have to write this code in a class or struct then create the object of the class or struct then you have to assign diameter value and print it.
/**
This code you can run in playground
*/
class Demo {
var radius:Double = 10
var diameter: Double {
get{
return radius * 2
}
set{
radius = newValue
}
}
}
let d = Demo()
d.diameter = 30
print(d.diameter)
//Output
60.0
/**
This code you can run in Xcode.
*/
class ViewController: UIViewController {
var radius:Double = 10
var diameter: Double {
get{
return radius * 2
}
set{
radius = newValue
}
}
override func viewDidLoad() {
super.viewDidLoad()
diameter = 30
print(diameter) // Output: 60.0
}
}