Pass dynamic data from parent view to child view in SwiftUI using MVVM architecture.

PassDynamicDataFromParentToChildView.swift

import SwiftUI
import Combine

struct ContentView: View {
    var body: some View {
        ParentView()
    }
}

struct ParentView: View {
    @StateObject var viewModel = ParentViewModel()

    var body: some View {
        VStack {
            Text("Random: \(viewModel.number)")

            Button("Random") {
                viewModel.random()
            }

            Divider()

            CounterView(random: viewModel.$number.eraseToAnyPublisher())
        }
    }
}

class ParentViewModel: ObservableObject {
    @Published var number: Int = 0

    func random() {
        number = Int.random(in: 0..<100)
    }
}

struct CounterView: View {
    @StateObject private var viewModel = CounterViewModel()
    let random: AnyPublisher<Int, Never>

    var body: some View {
        VStack {
            Text("Random: \(viewModel.random)")
            Text("Count: \(viewModel.count)")
            Text("Total: \(viewModel.total)")

            Button("Increase") {
                viewModel.increase()
            }
        }
        .onReceive(random) { value in
            viewModel.random = value
        }
    }
}

class CounterViewModel: ObservableObject {
    init() {
        $count
            .combineLatest($random)
            .map { count, random in
                return count + random
            }
            .assign(to: &$total)
    }

    @Published var count = 0
    @Published var random: Int = 0
    @Published var total: Int = 0

    func increase() {
        count += 1
    }
}