extension

UInt64

static

let

oneSecond

UInt64

1_000_000_000

enum

Weather

String

case

rainy

sunny

Next, define the view model and mark it as an ObservableObject 
so that it can return a value of type Weather?. 
Use GCD create to a DispatchQueue to 
send the work to the pool of threads

class

ContentViewModel

ObservableObject

@Published

private(set)

var

result

Weather

private

let

queue

DispatchQueue

label