Observableの効果範囲を検証するViewファイル

ObservableLifecycle.swift

//
//  ContentView.swift
//  StateObservable
//
//  Created by bannzai on 2025/03/09.
//

import SwiftUI

@Observable
final class Observed {
  var text = "Hello, world!"
}

struct ContentView: View {
  let observed = Observed()

  var body: some View {
    VStack {
      Text("ContentView:----")
      Button {
        observed.text = "Hello, ContentView!"
      } label: {
        Text(observed.text)
      }

      Text("VarObservable:----")
      VarObservable()

      Text("StateObservable:----")
      StateObservable()

      Text("EnvironmentObservable:----")
      EnvironmentObservable()
        .environment(observed)
    }
    .buttonStyle(.borderedProminent)
  }
}

struct VarObservable: View {
  let observed = Observed()

  var body: some View {
    Button {
      observed.text = "Hello, VarObservable!"
    } label: {
      Text(observed.text)
    }
  }
}

struct StateObservable: View {
  @State var observed = Observed()

  var body: some View {
    Button {
      observed.text = "Hello, StateObservable!"
    } label: {
      Text(observed.text)
    }
  }
}

struct EnvironmentObservable: View {
  @Environment(Observed.self) var observed: Observed

  var body: some View {
    Button {
      observed.text = "Hello, EnvironmentObservable!"
    } label: {
      Text(observed.text)
    }
  }
}

#Preview {
  ContentView()
    .frame(width: 400, height: 1000)
}