Capture previous value from textfield in SwiftUI - swiftui

Question

I am creating a basic manual counter to keep track of visitors, however, I am struggling to find out how I can capture and present the previous value entered by the user alongside the current number.
When I tap on the counter (0) (aka editednumber), a box appears and the user is asked to enter a number, I want to be able to save the number entered by the user, so when the user taps the counter again to enter a new number, the screen will show the previous number entered as well as the current number entered.
The previous number will of course be overwritten, every time a new number is entered, but regardless, I would like the previous number and new number to appear.
Example:
User enters the number 10, this will show as current_guests/editednumber which is fine, but if I tap to enter a new number 12, only the last entered number (10) is showing.
I want the view to show both the old (10) (stored into the previous_editednumber variable) and current (12) number (editednumber).
My code is as following:
// testView.swift
import SwiftUI
struct testView: View {
#State var current_guests:Int = 0
#State var denied_guests:Int = 0
#State var total_guests:Int = 0
#State var editednumber:Int = 0
#State var previous_editednumber:Int = 0
#State private var presentAlert = false
var body: some View {
VStack {
VStack {
Text("total_guests: \(total_guests)")
Text("current_guests: \(current_guests)")
Text("editednumber: \(editednumber)")
Text("previous_editednumber:\(previous_editednumber)")
Button("\(current_guests)") {
presentAlert = true
}
.alert("", isPresented: $presentAlert, actions: {
TextField("Number", value: $editednumber, formatter: NumberFormatter()).font(.system(size: 18)).foregroundColor(.black).multilineTextAlignment(.center).keyboardType(.numberPad)
Button("OK", action: {
// perform calculations based on input
if (editednumber >= total_guests) {
current_guests = editednumber
total_guests = editednumber + total_guests
}
if (editednumber < total_guests) {
current_guests = editednumber
total_guests = total_guests - current_guests
}
})
Button("Cancel", role: .cancel, action: {})
}, message: {
Text("Enter number of guests inside")
}).font(.system(size: 58, weight: .heavy)).keyboardType(.decimalPad) .frame(maxWidth: .infinity, alignment: .center).padding(.bottom,70).ignoresSafeArea(.keyboard)
}
// main buttons
HStack {
Button {
current_guests += 1
total_guests += 1
}label: {
Image(systemName: "plus")}.foregroundColor(.white).background(Color .green).frame(width: 80, height: 80).background(Color.green).font(.system(size: 50)).cornerRadius(40).padding()
Button {
denied_guests += 1
}label: {
Image(systemName: "nosign")}.foregroundColor(.white).background(Color .orange).frame(width: 80, height: 80).background(Color.orange).font(.system(size: 50)).cornerRadius(40).padding()
Button {
current_guests -= 1
if (current_guests <= 0) {
current_guests = 0
} }label: {
Image(systemName: "minus")}.foregroundColor(.white).background(Color .red).frame(width: 80, height: 80).background(Color.red).font(.system(size: 50)).cornerRadius(40).padding()
}
}
}
}
struct testView_Previews: PreviewProvider {
static var previews: some View {
testView()
}
}

Answer 1

You can create an in-between #State that takes its initial value from editednumber then returns the newValue when the user clicks "Ok".
struct AlertBody: View{
#State var newValue: Int
let onAccept: (Int) -> Void
let onCancel: () -> Void
init(initialValue: Int, onAccept: #escaping (Int) -> Void, onCancel: #escaping () -> Void){
self._newValue = State(initialValue: initialValue)
self.onAccept = onAccept
self.onCancel = onCancel
}
var body: some View{
TextField("Number", value: $newValue, formatter: NumberFormatter()).font(.system(size: 18)).foregroundColor(.black).multilineTextAlignment(.center).keyboardType(.numberPad)
Button("OK", action: {
onAccept(newValue)
})
Button("Cancel", role: .cancel, action: onCancel)
}
}
Then you can replace the content in the alert
struct HistoryView: View {
#State private var currentGuests:Int = 0
#State private var deniedGuests:Int = 0
#State private var totalGuests:Int = 0
#State private var editedNumber:Int = 0
#State private var previousEditedNumber:Int = 0
#State private var presentAlert = false
var body: some View {
VStack {
VStack {
Text("total_guests: \(totalGuests)")
Text("current_guests: \(currentGuests)")
Text("editednumber: \(editedNumber)")
Text("previous_editednumber:\(previousEditedNumber)")
Button("\(currentGuests)") {
presentAlert = true
}
.alert("", isPresented: $presentAlert, actions: {
AlertBody(initialValue: editedNumber) { newValue in
//Assign the previous number
previousEditedNumber = editedNumber
//Assign the newValue
editedNumber = newValue
//Your previous logic
if (editedNumber >= totalGuests) {
currentGuests = editedNumber
totalGuests = editedNumber + totalGuests
}
if (editedNumber < totalGuests) {
currentGuests = editedNumber
totalGuests = totalGuests - currentGuests
}
} onCancel: {
print("cancelled alert")
}
}, message: {
Text("Enter number of guests inside")
}).font(.system(size: 58, weight: .heavy)).keyboardType(.decimalPad) .frame(maxWidth: .infinity, alignment: .center).padding(.bottom,70).ignoresSafeArea(.keyboard)
}
// main buttons
HStack {
Button {
currentGuests += 1
totalGuests += 1
}label: {
Image(systemName: "plus")}.foregroundColor(.white).background(Color .green).frame(width: 80, height: 80).background(Color.green).font(.system(size: 50)).cornerRadius(40).padding()
Button {
deniedGuests += 1
}label: {
Image(systemName: "nosign")}.foregroundColor(.white).background(Color .orange).frame(width: 80, height: 80).background(Color.orange).font(.system(size: 50)).cornerRadius(40).padding()
Button {
currentGuests -= 1
if (currentGuests <= 0) {
currentGuests = 0
} }label: {
Image(systemName: "minus")}.foregroundColor(.white).background(Color .red).frame(width: 80, height: 80).background(Color.red).font(.system(size: 50)).cornerRadius(40).padding()
}
}
}
}