iOS-notes

Tiny Tips

How to use @available to deprecate old APIs

在闭包中强引用 self 的两种方法

// Proposal 1
class MyClass {
 prepareVideo {
 self.movePlayhead(to: self.video.lastPlayheadPosition)
 self.startPlaybackIfNeeded()
 }
}
// Proposal 2
class MyClass {
 prepareVideo { [self] in
 movePlayhead(to: video.lastPlayheadPosition)
 startPlaybackIfNeeded()
 }
}

SwiftUI 元素刷新

struct MyView: View {
 @State var text: String = ""
 
 var body: some View {
 Text(text)
 .onTapGesture {
 // 可以更新
 self.text = "Tapping..."
 }
 }
}
struct XXApp: App {
 var body: some Scene {
 WindowGroup <MyView> {
 let view = MyView()
 DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
 // 无法更新
 view.text = "Update text"
 }
 return view
 }
 }
}

struct MyView: View {
 @ObservedObject var viewModel: MyViewModel
 var body: some View {
 Text(viewModel.text)
 }
}
class MyViewModel: ObservableObject {
 @Published var text: String = ""
}
struct XXApp: App {
 var viewModel: MyViewModel = .init()
 var body: some Scene {
 WindowGroup <MyView> {
 let view = MyView(viewModel: viewModel)
 DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
 // 可以更新
 viewModel.text = "Update text"
 }
 return view
 }
 }

UICollectionView drag and drop

@discardableResult

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