Counter.swift

import SwiftUI

struct CounterView: View {
    // Data binding with CounterView Model
    @EnvironmentObject var counterViewModel: CounterViewModel

    var body: some View {
        return VStack {
            // count value updated automatically by data binding
            Text(String(self.counterViewModel.count))
            HStack {
                Button("+", action: {
                    self.counterViewModel.countUp()
                })
                Button("-", action: {
                    self.counterViewModel.countDown()
                })
            }
            // ✅ Stepper update value internally, and it works as Model
            //    So, we don't need to write model logic
            Stepper("Enter your age", value: self.$counterViewModel.count2, in: 0...130)
            Text(String(counterViewModel.count2))
        }
    }
}

struct CountView_Previews: PreviewProvider {
    static var previews: some View {
        CounterView().environmentObject(CounterViewModel())
    }
}

class CounterViewModel: ObservableObject {
    // Store count for view
    @Published var count = 0
    @Published var count2 = 0
    
    // Has countUp and countDown method for View
    public func countUp() {
        // Call CounterModel methods to increment and decrement count and update its count with returned value
        count = CounterModel.incrmentCount(currentCount: count)
    }
        

    public func countDown() {
        count = CounterModel.decrementCount(currentCount: count)
    }
}