Check if today is a new day SwiftUI - swift

Question

How can I check if today is a new day?
How can I say when the app lunches or in background, whichever, if it's 8am of a new day then do some action...
Date() would only give me the current date.
I need this to do some resetting and possibly to send notification at a specific time

Answer 1

you could try something like this:
import SwiftUI
struct ContentView: View {
#State var lastDay: Date = Date()
#State var isToday = false
#State var selectedTime = 8 // 24 hour clock
var body: some View {
Text("your main view")
.onReceive(NotificationCenter.default.publisher(for: UIApplication.willResignActiveNotification)) { _ in
// store the date whenever you go into background
print("---> storing: \(Date())")
UserDefaults.standard.set(Date(), forKey: "lastDay")
}
.onReceive(NotificationCenter.default.publisher(for: UIApplication.willEnterForegroundNotification)) { _ in
// try to retrieve the date when you come back from background
print("\n----> try retrieve lastDay")
if let temDate = UserDefaults.standard.object(forKey: "lastDay") {
self.lastDay = temDate as! Date
print("----> retrieved lastDay: \(self.lastDay)")
if Calendar.current.isDate(Date(), inSameDayAs: self.lastDay) {
self.isToday = true
print("----> isToday: \(self.isToday)\n")
// if it is 8 am or later do something
if let thisHour = Calendar.current.dateComponents([.hour], from: Date()).hour {
if (thisHour >= self.selectedTime) {
print("----> it is 8am or later --> do something")
// self.doSomething()
}
}
}
}
}
}
}
NotificationCenter is Apple internal message system. SwiftUI can listen for specific events, like when the App goes into the background. This is what this line does:
.onReceive(NotificationCenter.default.publisher(for: UIApplication.willResignActiveNotification))
Now, this line:
.onReceive(NotificationCenter.default.publisher(for: UIApplication.willEnterForegroundNotification))
listens for when you come back from the background, as mentioned in the comments.
There is no slowing down because of these onReceives.
What I have shown is an approach, you can add other .onReceive, such as:
.onReceive(NotificationCenter.default.publisher(for: UIApplication.didBecomeActiveNotification)) { _ in
.onReceive(NotificationCenter.default.publisher(for: UIApplication.willTerminateNotification)) { _ in
These can be used for when you start the App, and when you quit the App.

Answer 2

So this all should work to be able to tell if the date has changed.
struct ContentView: View {
#State private var lastDateString = UserDefaults.standard.string(forKey: "lastDateString") ?? String()
//stores lastDateString in memory for if the app closes
#State var lastDate = Date()
#State var currentDate = Date()
#State var currentDateString = String()
#State var differentDate = false;
let timer = Timer.publish(every: 1.0, on: .main, in: .common).autoconnect()
//Creates a timer that goes every 1 second
func newDay() {
let formatter = DateFormatter()
formatter.dateFormat = "d MM y"
//sets the format so it will be day month year
if lastDateString == String() {
lastDateString = formatter.string(from: lastDate)
UserDefaults.standard.set(self.lastDateString, forKey: "lastDateString")
} //sets initial value for lastDateString for first time app ever launches
self.currentDate = Date()
currentDateString = formatter.string(from: currentDate)
//sets currentDateString for every time app launches
if lastDateString != currentDateString {
self.differentDate = true
self.lastDate = Date()
self.currentDate = Date()
lastDateString = formatter.string(from: lastDate)
UserDefaults.standard.set(self.lastDateString, forKey: "lastDateString")
currentDateString = formatter.string(from: currentDate)
}
//checks if the date has changed and sets differentDate to true if it has
}
var body: some View {
VStack{
Text("Hello, World!")
.onAppear(){ //used to run function when app launches
self.newDay()
}
}
.onReceive(self.timer) { _ in
self.newDay()
} //calls function newDay() every second from timer
}
}
Hope this helps and sorry that this may not be the most concise, but hopefully it helps.

Answer 3

if Calendar.current.isDate(lastVisit as! Date, inSameDayAs: Date()) {
print("Same day")
} else {
print("New day")
}