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StateObject(wrappedValue:) を直接呼び出すと余計なオブジェクトを作る
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| import SwiftUI | |
| // MARK: - ObservableObject | |
| final class Counter: ObservableObject { | |
| @Published private(set) var count: Int | |
| deinit { | |
| print("🍂", #function, count) | |
| } | |
| init(count: Int = 1) { | |
| self.count = count | |
| print("🌱", #function, count) | |
| } | |
| func increment() { | |
| count += 1 | |
| } | |
| func reset() { | |
| count = 1 | |
| } | |
| } | |
| // MARK: - View | |
| struct ContentView: View { | |
| var body: some View { | |
| FooView() | |
| } | |
| } | |
| struct FooView: View { | |
| @StateObject var counter = Counter() | |
| var body: some View { | |
| VStack(spacing: 16) { | |
| HStack { | |
| ForEach(0..<counter.count, id: \.self) { offset in | |
| BarView(counter: Counter(count: offset+1)) | |
| } | |
| } | |
| Button("Increment") { counter.increment() } | |
| Button("Reset") { counter.reset() } | |
| } | |
| } | |
| } | |
| struct BarView: View { | |
| @StateObject var counter: Counter | |
| // // ⛔️ 余計なオブジェクトを作る | |
| // init(counter: Counter) { | |
| // _counter = StateObject(wrappedValue: counter) | |
| // } | |
| // // 🤓 余計なオブジェクトはつくらない。リファレンスでは直接よぶべきではないとしているので利用は避けたほうがよいかも？💭 | |
| // // https://developer.apple.com/documentation/swiftui/stateobject/init(wrappedvalue:) | |
| // init(counter: @escaping @autoclosure () -> Counter) { | |
| // _counter = StateObject(wrappedValue: counter()) | |
| // } | |
| var body: some View { | |
| Text(counter.count.formatted()) | |
| .foregroundColor(.mint) | |
| } | |
| } | |
| // MARK: - PreviewProvider | |
| struct ContentView_Previews: PreviewProvider { | |
| static var previews: some View { | |
| ContentView() | |
| } | |
| } |
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