How to call API only once in 30min in swift5? - ios

Question

I am calling one API, but that data is not changing frequently and I am storing data in core data. I want that API should call only once in 30 min. is there any better approach of calling API only if it exceed 30 min from last API call. I can think of Timer based, but like to know if there is any other better way to do same?

Answer 1

If you are calling the api randomly then holding a variable in memory for the last successful call might be good enough. If you want the API to be called automatically you'll best approach would be to set up a timer.
If you want your app to prohibit to make a new call in 30 min, then this would be a quick example:
(wrote this for a playground)
var lastCheck: Date?
let minimumMinutes = 60.0
func makeNetworkCall() {
if let lastCheckDate = lastCheck, lastCheckDate.timeIntervalSinceNow < (30 * minimumMinutes) {
debugPrint("Not making call, Didn't go 30 min yet")
return
}
lastCheck = Date()
debugPrint("Making network call!")
// ... make call
}
makeNetworkCall() // Should make call
makeNetworkCall() // Should not make call
makeNetworkCall() // Should not make call
I haven't tested the code above, but it should work.

Answer 2

To just limit service calling for a specific time (ex 30 minutes), you can store last service called date and use it to decide to do a call or not. You can store the date in memory or persistent storage depend on you need.
UserDefaults can be an option to store last date for persistance. There is a sample implementation below;
func saveLastServiceCalledDate() {
UserDefaults.standard.set(Date(), forKey: "lastServiceCallDate")
}
func isCalledInLast30Min() -> Bool {
guard let lastDate = UserDefaults.standard.value(forKey: "lastServiceCallDate") as? Date else { return false }
let timeElapsed: Int = Int(Date().timeIntervalSince(lastDate))
return timeElapsed < 30 * 60 // 30 minutes
}
func serviceCall() {
// ignore if called in last 30 minutes
if isCalledInLast30Min() { return }
// save current date
saveLastServiceCalledDate()
// do service call
}

Answer 3

My suggestion is to use DispatchSourceTimer because it can be restarted at any time.
Call startTimer() in viewDidLoad and in applicationWillBecomeActive to get the most recent data when the application becomes active
var timer : DispatchSourceTimer!
func startTimer()
{
if timer == nil {
timer = DispatchSource.makeTimerSource(queue: DispatchQueue.global())
timer.schedule(deadline: .now(), repeating: 30.0)
timer.setEventHandler {
self.callAPI()
}
timer.activate()
} else {
timer.schedule(deadline:.now(, repeating: 30.0)
}
}

Answer 4

There is no way but timer
1- Create a Timer with 1 minute schedule
2- Timer function checks current timeStamp against a stored 1 say in defaults
3- If stored value is nil or exceeded 30 minutes gap between the current call the api
4- When you call the api update the stored value with the current 1
The reason behind making it a stored value not global is freguently opening and closing the app won't cause non-new api calls
let current = Date().timeIntervalSince1970
let stored = UserDefaults.standard.double(forKey:"stored")
if stored == 0 || current - stored >= 30.0 {
// call the api && update stored value
}

Answer 5

You haven't mentioned whether this should happen in background or foreground? Because based on that only we need to go for the solution. In case if u are wondering about update the data in the background, you should check apples BGTaskBackground. But the problem with this is, you can't decide the time to trigger. You can only give minimumFetchingInterval, which is not guaranteed but will be decided by the system/is.
Incase if you are looking to update in the foreground, just go with the timer approach you are talking about. Use any background queues to do that job. Queues will help you out in dispatching specific task at specific time with delay method.