CODESAMPLE

Master-Slave - Swift

Master-Slave Swift

The Master-Slave pattern (also known as Leader-Follower) involves one object (the Master) holding the primary data and logic, while other objects (the Slaves) maintain copies of that data and react to changes propagated from the Master. This ensures consistency across multiple views or components. Here, the Master manages a list of items and notifies Slaves (in this case, SlaveView instances) whenever the list is updated. Swift’s Combine framework is used for reactive updates, fitting the language’s modern, declarative style. The Published property wrapper automatically broadcasts changes to subscribers, and the sink operator allows SlaveView to react to those changes.

import Combine

class Item: Identifiable {
    let id = UUID()
    var name: String
    
    init(name: String) {
        self.name = name
    }
}

class Master: ObservableObject {
    @Published var items: [Item] = []

    func addItem(name: String) {
        items.append(Item(name: name))
    }
}

struct SlaveView: View {
    @ObservedObject var master: Master
    var index: Int

    var body: some View {
        Text("Item \(index + 1): \(master.items[index].name)")
    }
}

struct ContentView: View {
    @StateObject var master = Master()

    var body: some View {
        VStack {
            Button("Add Item") {
                master.addItem(name: "New Item \(master.items.count + 1)")
            }
            
            if !master.items.isEmpty {
                ForEach(0..<master.items.count, id: \.self) { i in
                    SlaveView(master: master, index: i)
                }
            } else {
                Text("No items yet.")
            }
        }
    }
}