Discover Observation in SwiftUI

1:26 - Using @Observable

@Observable class FoodTruckModel {    
    var orders: [Order] = []
    var donuts = Donut.all
}

2:12 - SwiftUI property tracking

@Observable class FoodTruckModel {    
  var orders: [Order] = []
  var donuts = Donut.all
}

struct DonutMenu: View {
  let model: FoodTruckModel
    
  var body: some View {
    List {
      Section("Donuts") {
        ForEach(model.donuts) { donut in
          Text(donut.name)
        }
        Button("Add new donut") {
          model.addDonut()
        }
      }
    }
  }
}

3:12 - SwiftUI computed property tracking

@Observable class FoodTruckModel {    
  var orders: [Order] = []
  var donuts = Donut.all
  var orderCount: Int { orders.count }
}

struct DonutMenu: View {
  let model: FoodTruckModel
    
  var body: some View {
    List {
      Section("Donuts") {
        ForEach(model.donuts) { donut in
          Text(donut.name)
        }
        Button("Add new donut") {
          model.addDonut()
        }
      }
      Section("Orders") {
        LabeledContent("Count", value: "\(model.orderCount)")
      }
    }
  }
}

4:41 - Using @State

struct DonutListView: View {
    var donutList: DonutList
    @State private var donutToAdd: Donut?

    var body: some View {
        List(donutList.donuts) { DonutView(donut: $0) }
        Button("Add Donut") { donutToAdd = Donut() }
            .sheet(item: $donutToAdd) {
                TextField("Name", text: $donutToAdd.name)
                Button("Save") {
                    donutList.donuts.append(donutToAdd)
                    donutToAdd = nil
                }
                Button("Cancel") { donutToAdd = nil }
            }
    }
}

5:14 - Using @Environment

@Observable class Account {
  var userName: String?
}

struct FoodTruckMenuView : View {
  @Environment(Account.self) var account

  var body: some View {
    if let name = account.userName {
      HStack { Text(name); Button("Log out") { account.logOut() } }
    } else {
      Button("Login") { account.showLogin() }
    }
  }
}

6:27 - Using @Bindable

@Observable class Donut {
  var name: String
}

struct DonutView: View {
  @Bindable var donut: Donut

  var body: some View {
    TextField("Name", text: $donut.name)
  }
}

7:53 - Storing @Observable types in Array

@Observable class Donut {
  var name: String
}

struct DonutList: View {
  var donuts: [Donut]
  var body: some View {
    List(donuts) { donut in
      HStack {
        Text(donut.name)
        Spacer()
        Button("Randomize") {
          donut.name = randomName()
        }
      }
    }
  }
}

9:18 - Manual Observation

@Observable class Donut {
  var name: String {
    get {
      access(keyPath: \.name)
      return someNonObservableLocation.name 
    }
    set {
      withMutation(keyPath: \.name) {
        someNonObservableLocation.name = newValue
      }
    }
  } 
}