Signal4.swift

//Create an observer
let signalObserver = Signal<Int, NoError>.Observer(
value: { value in
    print("Time elapsed = \(value)")
}, completed: { 
    print("completed") 
}, interrupted: { 
    print("interrupted") 
})
//Create an a signal
let (output, input) = Signal<Int, NoError>.pipe()
//Send value to signal
for i in 0..<10 {
    DispatchQueue.main.asyncAfter(deadline: .now() + 5.0 *  Double(i)) {
  input.send(value: i)
 }
}
//Observe the signal
output.observe(signalObserver)