Display function output live without Button press - swift

Question

My Swift UI code currently calls a function to display calculations upon a button call. I'd like to display the function's output without the button call (in other words, the function is "live" and constantly calculating anytime a necessary variable is changed). Basically, I'm looking to get rid of the button that triggers this function call calculation, and always have the function's display shown. It has default values so it should have info even before the user inputs or something is changed.
The first screenshot shows the code currently, and the second shows where I'd like the time calculation string to always be. Note: this uses a Create ML file, so if you're inputting this code into your editor, it's not necessary to have the model use to calculate. Any use and output of the variables will do and I've left some commented code that might help.
I'm thinking there might be a calculate on change of X, Y, Z variable needed here. I'm not sure the best way to approach this and would love any ideas. Thanks!
import CoreML
import SwiftUI
struct ContentView: View {
#State var wakeUpTime = defaultWakeTime
#State var coffeeAmount = 1.0
#State var sleepAmount = 8.0
#State var alertTitle = ""
#State var alertMessage = ""
#State var showAlert = false
static var defaultWakeTime: Date {
var components = DateComponents()
components.hour = 7
components.minute = 0
return Calendar.current.date(from: components) ?? Date.now
}
var body: some View {
NavigationView {
Form {
Section {
DatePicker("Please enter a time", selection: $wakeUpTime, displayedComponents: .hourAndMinute)
.labelsHidden()
} header: {
Text("When do you want to wake up?")
.font(.headline)
}
VStack(alignment: .leading, spacing: 0) {
Text("Hours of sleep?")
.font(.headline)
Stepper(sleepAmount == 1 ? "1 hour" : "\(sleepAmount.formatted()) hours", value: $sleepAmount, in: 1...12, step: 0.25)
}
VStack(alignment: .leading, spacing: 0) {
Text("Cups of coffee?")
.font(.headline)
Stepper(coffeeAmount == 1 ? "1 cup" : "\(coffeeAmount.formatted()) cups", value: $coffeeAmount, in: 1...12, step: 0.25)
}
Section {
Text("Head to bed at: IDEAL TIME HERE")
}
}
.navigationTitle("BetterRest")
.toolbar {
Button("Calculate", action: calculateBedtime)
}
.alert(alertTitle, isPresented: $showAlert) {
Button("Ok") { }
} message: {
Text(alertMessage)
}
}
}
func calculateBedtime() {
do {
let config = MLModelConfiguration()
let model = try SleepCalculator(configuration: config)
let components = Calendar.current.dateComponents([.hour, .minute], from: wakeUpTime)
let hour = (components.hour ?? 0) * 60 * 60
let minute = (components.minute ?? 0) * 60
let predicition = try model.prediction(wake: Double(hour + minute), estimatedSleep: sleepAmount, coffee: Double(coffeeAmount))
let sleepTime = wakeUpTime - predicition.actualSleep
alertTitle = "Your ideal bedtime is..."
alertMessage = sleepTime.formatted(date: .omitted, time: .shortened)
}
catch {
alertTitle = "Error"
alertMessage = "Sorry. There was a problem calculating your bedtime."
}
showAlert = true
// IF TRYING WITHOUT CREATE ML MODEL, comment out all of above^
// let alertTitle = "Showing calculated title"
// let alertMessage = "7:15 am"
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}

Answer 1

you could try this approach, where you create a class BedTimeModel: ObservableObject to
monitor changes in the various variables that is used to calculate (dynamically)
your sleepTime using func calculateBedtime().
EDIT-1: using Optional sleepTime
class BedTimeModel: ObservableObject {
#Published var sleepTime: Date? = Date() // <-- here optional
#Published var wakeUpTime = defaultWakeTime {
didSet { calculateBedtime() }
}
#Published var coffeeAmount = 1.0 {
didSet { calculateBedtime() }
}
#Published var sleepAmount = 8.0 {
didSet { calculateBedtime() }
}
// can also change this to return the calculated value and use it to update the `sleepTime`
func calculateBedtime() {
// do {
// let config = MLModelConfiguration()
// let model = try SleepCalculator(configuration: config)
// let components = Calendar.current.dateComponents([.hour, .minute], from: wakeUpTime)
// let hour = (components.hour ?? 0) * 60 * 60
// let minute = (components.minute ?? 0) * 60
// let predicition = try model.prediction(wake: Double(hour + minute), estimatedSleep: sleepAmount, coffee: Double(coffeeAmount))
//
// sleepTime = wakeUpTime - predicition.actualSleep // <-- here
// }
// catch {
// sleepTime = nil // <-- here could not be calculated
// }
// for testing, adjust the real calculation to update sleepTime
sleepTime = wakeUpTime.addingTimeInterval(36000 * (sleepAmount + coffeeAmount))
}
static var defaultWakeTime: Date {
var components = DateComponents()
components.hour = 7
components.minute = 0
return Calendar.current.date(from: components) ?? Date.now
}
}
struct ContentView: View {
#StateObject private var vm = BedTimeModel() // <-- here
var body: some View {
NavigationView {
Form {
Section {
DatePicker("Please enter a time", selection: $vm.wakeUpTime, displayedComponents: .hourAndMinute)
.labelsHidden()
} header: {
Text("When do you want to wake up?").font(.headline)
}
VStack(alignment: .leading, spacing: 0) {
Text("Hours of sleep?").font(.headline)
Stepper(vm.sleepAmount == 1 ? "1 hour" : "\(vm.sleepAmount.formatted()) hours", value: $vm.sleepAmount, in: 1...12, step: 0.25)
}
VStack(alignment: .leading, spacing: 0) {
Text("Cups of coffee?").font(.headline)
Stepper(vm.coffeeAmount == 1 ? "1 cup" : "\(vm.coffeeAmount.formatted()) cups", value: $vm.coffeeAmount, in: 1...12, step: 0.25)
}
Section {
// -- here
if let stime = vm.sleepTime {
Text("Head to bed at: \(stime.formatted(date: .omitted, time: .shortened))")
} else {
Text("There was a problem calculating your bedtime.")
}
}
}
.navigationTitle("BetterRest")
}
}
}