Command Line Tool using Timer() in Swift - swift

Question

I'm writing a command line tool and want to handle various inputs and also want to fire a Timer() on a specific command and also stop it on an other command.
Unfortunately this does not work
import Foundation
class timerTest : NSObject {
var myTimer : Timer? = nil
func startTimer() {
myTimer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true, block: {_ in
print("Hello")
})
let runLoop = RunLoop()
runLoop.add(myTimer!, forMode: .defaultRunLoopMode)
RunLoop.current.run()
}
func stopTimer() {
myTimer?.invalidate()
}
}
var a = timerTest()
print("Ready")
while true {
var keyboard = FileHandle.standardInput
var inputData = keyboard.availableData
var string = NSString(data: inputData, encoding:String.Encoding.utf8.rawValue) as! String
string = string.trimmingCharacters(in: .whitespacesAndNewlines)
if string == "timer" { a.startTimer() }
if string == "stop" { a.stopTimer() }
}

Answer 1

You can use something like this:
import Foundation
var shouldKeepRunning = true
class CLIInput:NSObject {
var inputTimer:Timer? = nil
var myTimer:Timer? = nil
func getInput() {
inputTimer = Timer.scheduledTimer(withTimeInterval:1, repeats:false, block: {_ in
var input = readLine()!
input = input.trimmingCharacters(in: .whitespacesAndNewlines)
print("Input: \(input)")
if input == "timer" {
print("Start timer")
self.myTimer = Timer.scheduledTimer(withTimeInterval:1, repeats: true, block: {_ in
print("Hello")
})
}
if input == "stop" {
print("Stop timer")
self.myTimer?.invalidate()
self.myTimer = nil
}
if input == "exit" {
print("Time to exit")
self.inputTimer?.invalidate()
self.inputTimer = nil
shouldKeepRunning = false
return
}
// Otherwise, set up timer again
self.getInput()
})
}
}
print("Start")
var cli = CLIInput()
cli.getInput()
let theRL = RunLoop.current
while shouldKeepRunning && theRL.run(mode: .defaultRunLoopMode, before: .distantFuture) { }
However, any time you are waiting for input from standard input, you'll find that your timer block output does not display because output is blocked till your input is complete. As long as your timer process does not need to do any output, the above might (or might not, depending on your requirements) work ...