Trigger UIAlertViewController Based on Time - ios

Question

I have UITable to display different animals. When you select a cell in the table, a new view controller with a large UIImage is pushed. Currently, when you zoom in on the image, a UIAlertView is triggered that asks the user if they would like to download hi res images. If they click yes, the "hi-res-flag" is set to "yes" in user defaults and they no longer see the pop up. However, if they select no, the hi-res-flag will continue to pop up each time they zoom in on a photo.
Instead, if they answer no, I would like to have this flag pop up occasionally. Not every time the click a cell in the species table, nor every time they open the app. Something more like once or twice a month. Is there a way to use time in the logic of an iOS app? For instance, erase the value set for "high-res-flag" (if already equals 'no') in user defaults, once a month?

Answer 1

Store the time you showed the alert last in the user preferences, and then check that value every time before you present the alert whether a certain time has passed.

Answer 2

I have written a time checker class that does the job. The code is in Swift. You can use it from your Objective-C code as well. You can find this code in gist here.
Solution
Below, you use the viewWillAppear delegate method to see if the hiResFlag is existing. If it is present and false, then you check to see if you can display the popup:
import UIKit
class ImageViewController: UIViewController {
//Whenever you enter the Image View Controller, you check whether to show popup or not
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
if let hiResFlag = hiResFlag {
if hiResFlag == false {
if PopUpTimeChecker.shouldShowPopUp() {
self.presentAlert()
}
}
}
}
func presentAlert() {
let alert = UIAlertController.init(title: nil, message: "Show Pop up", preferredStyle: .alert)
let action = UIAlertAction.init(title: "Yeahh!", style: .default, handler: nil)
alert.addAction(action)
self.present(alert, animated: true, completion: nil)
}
}
The following code implements the time-checking algorithm. Edit popUpTimeInterval below for setting your minimum time. Right now, it is set to be 15 days (in seconds). Once in every 15 days the pop-up will be shown when you call the shouldShowPopUp method.
import UIKit
//Below 4 variables, I have made them Global. No need to make them global in your case
#objc var popUpTimeInterval: UInt64 = 1296000 //15 days in seconds
#objc var hiResFlag: Bool? {
get {
return UserDefaults.standard.object(forKey: "HiResFlag") as? Bool
}
set {
UserDefaults.standard.setValue(newValue, forKey: "HiResFlag")
}
}
#objc var isFirstTimePopUp: Bool {
get {
let value = UserDefaults.standard.object(forKey: "IsFirstTimePopUp")
return value == nil ? true : value as! Bool
}
set {
UserDefaults.standard.setValue(newValue, forKey: "IsFirstTimePopUp")
}
}
#objc var lastDateOfPopUp: Date? {
get {
return UserDefaults.standard.object(forKey: "LastDateOfPopUp") as? Date
}
set {
UserDefaults.standard.setValue(newValue, forKey: "LastDateOfPopUp")
}
}
#objc class PopUpTimeChecker {
#objc static fileprivate func setLastPopUpDate() {
//Setting current date to last shown pop up date
lastDateOfPopUp = Date()
}
#objc static fileprivate func timeIntervalSinceLastPopUp() -> UInt64 {
//Returning how much time (in seconds) has passed from last popup date until now
return UInt64(Date().timeIntervalSince(lastDateOfPopUp!))
}
#objc static func shouldShowPopUp() -> Bool {
//We proceed further only if we have the last date when pop up was displayed, else we create and set it as the current date
if let _ = lastDateOfPopUp {
let timeInterval = timeIntervalSinceLastPopUp()
if timeInterval > popUpTimeInterval {
self.setLastPopUpDate()
return true //Show pop up
} else {
if isFirstTimePopUp {
//If this is the first time, you just allow the pop up to show, don't allow otherwise
isFirstTimePopUp = false
return true
} else {
return false
}
}
} else {
self.setLastPopUpDate() //Since we don't have a last date, we set it here for starting off
return self.shouldShowPopUp() //Recursively call method
}
}
}