Exploring SwiftUI’s Data Flow

app-storage.swift

struct ContentView: View {
  @AppStorage("username") var username: String = "guest"

  var body: some View {
    VStack {
      Text("Welcome, \(username)!")
      TextField("Enter your username", text: $username)
    }
  }
}

binding.swift

struct MyView: View {
  @State var myState = "Hello, world!"

  var body: some View {
    TextField("Enter some text", text: $myState)
  }
}

enviroment-object.swift

class UserData: ObservableObject {
  @Published var name: String = "John"
  @Published var age: Int = 30
}

struct ContentView: View {
  @EnvironmentObject var userData: UserData

  var body: some View {
    VStack {
      Text("Name: \(userData.name)")
      Text("Age: \(userData.age)")
      ChildView()
    }
  }
}

struct ChildView: View {
  @EnvironmentObject var userData: UserData

  var body: some View {
    VStack {
      Text("Name: \(userData.name)")
      Text("Age: \(userData.age)")
    }
  }
}

observable-object.swift

class MyModel: ObservableObject {
  @Published var items: [String] = []
  @Published var selectedItem: String?
}

struct MyMasterView: View {
  @StateObject var model: MyModel

  var body: some View {
    List(model.items) { item in
      Text(item)
        .onTapGesture {
          model.selectedItem = item
        }
    }
  }
}

state.swift

@State var myState = "Hello, world!"