{"id":2825,"date":"2025-11-24T13:11:05","date_gmt":"2025-11-24T04:11:05","guid":{"rendered":"https:\/\/www.freelifemakers.org\/wordpress\/?p=2825"},"modified":"2025-11-24T20:47:28","modified_gmt":"2025-11-24T11:47:28","slug":"swift-sharing-ui-state-and-variables","status":"publish","type":"post","link":"https:\/\/www.freelifemakers.org\/wordpress\/index.php\/2025\/11\/24\/swift-sharing-ui-state-and-variables\/","title":{"rendered":"[Swift]UI\uc0c1\ud0dc\uc640 \ubcc0\uc218\ub97c \uacf5\uc720\ud558\uae30 \/ Sharing UI state and variables"},"content":{"rendered":"\n

\ud83d\udc49\ud83c\udffb \ud504\ub85c\uc81d\ud2b8 \uba85\uc774 PublisherSubscribe\uc778 \uacbd\uc6b0 \uc785\ub2c8\ub2e4.
If the project name is PublisherSubscribe.<\/p>\n\n\n\n

\ud83d\udc49\ud83c\udffb SwiftUI\uc5d0\uc11c @Publisher, @StateObject ,@ObservedObject\ub97c \ud1b5\ud574\uc11c \ubcc0\uc218\ub098 \uc0c1\ud0dc\ub97c \uacf5\uc720\ud569\ub2c8\ub2e4.
In SwiftUI, variables and states are shared through @Publisher, @StateObject, and @ObservedObject.<\/p>\n\n\n\n

\ud83d\udc49\ud83c\udffbSwiftUI\uc5d0\uc11c \ubdf0\uc758 \uac1c\ub150\uc740 struct {} \uad6c\uc870\ub85c\uc368 \ud654\uba74\uc5d0 \ubcf4\uc5ec\uc9c0\ub294 \uae30\ub2a5\uc744 \uac00\uc9c0\uace0 \uc788\ub294 \uac83\uc785\ub2c8\ub2e4.
In SwiftUI, the concept of a view is a struct {} structure that has the functionality to be displayed on the screen.<\/p>\n\n\n\n

\u2714\ufe0f@Publisher :
ObservableObject \uc548\uc5d0\uc11c \uc0ac\uc6a9\ud558\ub294 property wrapper\uc785\ub2c8\ub2e4.
View\uc5d0\uc11c @ObservedObject\ub098 @StateObject\ub85c \uc774 ViewModel\uc744 \uad00\ucc30\ud558\uba74 UI\uac00 \uc790\ub3d9 \uac31\uc2e0\ub429\ub2c8\ub2e4.<\/p>\n\n\n\n

This is a property wrapper used within ObservableObject. When the View observes this ViewModel using @ObservedObject or @StateObject, the UI is automatically updated.<\/p>\n\n\n\n

\u2714\ufe0f @StateObject :
ViewModel \uac19\uc740 \ucc38\uc870 \ud0c0\uc785 \uc0c1\ud0dc\ub97c View \uc7ac\uc0dd\uc131\uc5d0\ub3c4 \uc720\uc9c0\ud569\ub2c8\ub2e4.
Maintains reference type state, such as ViewModel, even when View is recreated.<\/p>\n\n\n\n

\uadf8\ub7ec\uba74 View\ub294 \uc5b8\uc81c \uc7ac\uc0dd\uc131 \ub418\ub098?
So when is the View regenerated?<\/p>\n\n\n\n

1)State\ub098 Binding\uc774 \ubc14\ub014 \ub54c \/ When State or Binding changes<\/p>\n\n\n\n

2)\ubd80\ubaa8 View\uac00 \uc5c5\ub370\uc774\ud2b8 \ub420 \ub54c \/ When the parent View is updated<\/p>\n\n\n\n

3)\ud654\uba74 rotation, layout change \ub4f1\uc774 \ubc1c\uc0dd\ud560 \ub54c \/ When screen rotation, layout change, etc. occur<\/p>\n\n\n\n

\u2714\ufe0f@ObservedObject :
\uc678\ubd80\uc5d0\uc11c \uc804\ub2ec\ubc1b\uc544 \uad00\ucc30\ub9cc, \uc7ac\uc0dd\uc131 \uc2dc \uac1d\uccb4 \uc18c\uc720\uad8c \uc5c6\uc2b5\ub2c8\ub2e4.
Observe only when received from outside, no ownership of object when recreated.<\/p>\n\n\n\n

\u2714\ufe0fObservableObject\ub294 ViewModel\uc774 UI\uc5d0\uac8c \u201c\ub0b4\uac00 \ubcc0\ud588\uc73c\ub2c8 \ub2e4\uc2dc \uadf8\ub824\ub2ec\ub77c\u201d\ub77c\uace0 \uc54c\ub9b4 \uc218 \uc788\uac8c \ud558\ub294 SwiftUI \uc804\uc6a9 \ud504\ub85c\ud1a0\ucf5c\uc785\ub2c8\ub2e4.
ObservableObject is a SwiftUI-specific protocol that allows a ViewModel to tell the UI, \u201cI changed, so redraw me.\u201d<\/p>\n\n\n\n

\ud83d\udc49\ud83c\udffb \uc774 \uc571\uc740 \ubc84\ud2bc\uc744 \ub204\ub97c \uacbd\uc6b0 \ubd80\ubaa8 \ubdf0\uc640 \uc790\uc2dd \ubdf0\uc5d0\uc11c \uce74\uc6b4\ud130 \uac12\uc774 \ub3d9\uc77c\ud558\uac8c \uc99d\uac00\ud558\ub294 \uc571\uc785\ub2c8\ub2e4.
This app is one that increases the counter value equally in both the parent view and child view when a button is pressed.<\/p>\n\n\n\n

2.\ucf54\ub4dc\/Code<\/strong><\/p>\n\n\n\n

\u2714\ufe0f PublisherSubscribeApp.swift<\/p>\n\n\n\n

\ubcf4\ud1b5 \uc774 \ud30c\uc77c\uc740 \ucc38\uc870\uc6a9\uc785\ub2c8\ub2e4. \uc790\ub3d9\uc0dd\uc131\ub418\uae30\ub54c\ubb38\uc5d0 \uc218\uc815\ud558\uc9c0 \uc54a\uc544\ub3c4 \ub429\ub2c8\ub2e4.
This file is usually for reference only. It is automatically generated and does not need to be modified.<\/p>\n\n\n\n

import SwiftUI\n\n@main\nstruct PublisherSubscribeApp: App {\n    var body: some Scene {\n        WindowGroup {\n            ContentView()\n        }\n    }\n}<\/code><\/pre>\n\n\n\n
\u2714\ufe0f ContentView.swift<\/p>\n\n\n\n
import SwiftUI\n\nstruct ContentView: View {\n    var body: some View {\n        VStack {\n            Image(systemName: \"globe\")\n                .imageScale(.large)\n                .foregroundStyle(.tint)\n            Text(\"Hello, world!\")\n            \n            ParentView()\n        }\n        .padding()\n    }\n}\n\n#Preview {\n    ContentView()\n}\n<\/code><\/pre>\n\n\n\n
\u2714\ufe0f ParentView.swift<\/p>\n\n\n\n
import SwiftUI\n\nstruct ParentView: View {\n    \n    \/\/ @StateObject \u2192 ViewModel\uc744 \"\uc774 View\uc5d0\uc11c \uc0dd\uc131\ud558\uace0 \ubcf4\uc720\"\ud568\n    \/\/ ViewModel\uc744 \uc9c1\uc811 \uc0ac\uc6a9\ud560 \uacbd\uc6b0 @StateObject\uc0ac\uc6a9 \ud568\n    \n    \/\/ @StateObject \u2192 \"Create and hold the ViewModel in this View\"\n    \/\/ Use @StateObject when using the ViewModel directly.\n    \n    @StateObject var viewModel = CounterViewModel()\n    \n    var body: some View {\n        VStack(spacing: 20) {\n            Text(\"Parent View Count: \\(viewModel.count)\")\n                .font(.title)\n            \n            Button(\"Increase\") {\n                viewModel.increase()\n            }\n            \n            \/\/ \uc790\uc2dd\uc5d0\uac8c ViewModel \uc804\ub2ec\n            ChildView(viewModel: viewModel)\n        }\n        .padding()\n    }\n}<\/code><\/pre>\n\n\n\n
\u2714\ufe0f ChildView.swift<\/p>\n\n\n\n
import SwiftUI\n\n\/\/ ParentView\uc5d0 \ud3ec\ud568\ub418\ub294 \ubdf0\nstruct ChildView: View {\n    \/\/ @ObservedObject \u2192 \ubd80\ubaa8\uc5d0\uc11c \uc804\ub2ec\ubc1b\uc740 ViewModel\uc744 \"\uad00\ucc30\"\ub9cc \ud568\n    \/\/ \uc790\uc2dd \ubdf0\uac00 \ubd80\ubaa8 \ubdf0\uc5d0\uac8c\uc11c ViewModel\uc744 \uc804\ub2ec \ubc1b\uc740\uacbd\uc6b0 @ObservedObject\ub97c \uc0ac\uc6a9\ud568.\n    @ObservedObject var viewModel: CounterViewModel\n    \n    var body: some View {\n        VStack(spacing: 10) {\n            Text(\"Child View Count: \\(viewModel.count)\")\n                .font(.headline)\n            \n            Button(\"Increase from Child\") {\n                viewModel.increase()\n            }\n        }\n        .padding()\n        .border(Color.gray)\n    }\n}<\/code><\/pre>\n\n\n\n
\u2714\ufe0f CounterViewModel<\/p>\n\n\n\n
import Foundation\nimport Combine\n\n\/\/ ObservableObject\ub294 ViewModel\uc774 UI\uc5d0\uac8c \u201c\ub0b4\uac00 \ubcc0\ud588\uc73c\ub2c8 \ub2e4\uc2dc \uadf8\ub824\ub2ec\ub77c\u201d\ub77c\uace0 \uc54c\ub9b4 \uc218 \uc788\uac8c \ud558\ub294 SwiftUI \uc804\uc6a9 \ud504\ub85c\ud1a0\ucf5c\uc785\ub2c8\ub2e4.\n\/\/ SwiftUI\uc5d0\uc11c ObservableObject\ub294 **\u201c\uc678\ubd80\uc5d0\uc11c \uad00\ucc30 \uac00\ub2a5\ud55c \uac1d\uccb4\u201d**\ub97c \ub9cc\ub4e4\uae30 \uc704\ud55c \ud504\ub85c\ud1a0\ucf5c\uc785\ub2c8\ub2e4.\n\n\/\/ ObservableObject is a SwiftUI-specific protocol that allows the ViewModel to tell the UI, \"I changed, so please redraw me.\"\n\/\/ In SwiftUI, ObservableObject is a protocol for creating \"objects that are observable from the outside\".\n\nclass CounterViewModel: ObservableObject {\n    \n    \/\/ @Published: \uac12\uc774 \ubc14\ub00c\uba74 \uc774\ubca4\ud2b8\ub97c \ub0b4\ubcf4\ub0b4\ub294 Publisher\n    \/\/ @Published: Publisher that emits an event when the value changes\n    \n    @Published var count: Int = 0\n    \n    func increase() {\n        count += 1\n    }\n}\n\n\/*\n \n @Published = objectWillChange.send()\ub97c \uc790\ub3d9\uc73c\ub85c \ud638\ucd9c\ud574\uc8fc\ub294 \ud3b8\uc758 \uae30\ub2a5\uc785\ub2c8\ub2e4.\n \uc6d0\ub798\ub294 \uc9c1\uc811 objectWillChange.send()\ub97c \ud638\ucd9c\ud558\uba74, @Published \uc5c6\uc774\ub3c4 UI\ub97c \uc5c5\ub370\uc774\ud2b8 \uac00\ub2a5\ud569\ub2c8\ub2e4.\n \ub2e8, \uac1c\ubc1c\uc790\uac00 \uac12\uc774 \ubc14\ub014 \ub54c\ub9c8\ub2e4 send()\ub97c \uc9c1\uc811 \ud638\ucd9c\ud574\uc57c \ud569\ub2c8\ub2e4.\n \uc774\ub7f0 \ubd80\ubd84\uc744 \uc790\ub3d9\uc73c\ub85c \ucc98\ub9ac\ud574\uc8fc\ub294\uac8c @Published\uc785\ub2c8\ub2e4.\n \n @Published is a convenience feature that automatically calls objectWillChange.send().\n Originally, if you call objectWillChange.send() directly, you can update the UI without @Published .\n However, developers must manually call send() every time a value changes.\n @Published handles this automatically.\n \n *\/<\/code><\/pre>\n\n\n\n
\u2714\ufe0f \uc2a4\ud06c\ub9b0\uc0f7 \/ ScreenShot<\/p>\n\n\n\n
\n