CoreData:为什么在book.isPublic切换时不刷新UI [英] CoreData: why not refresh UI when book.isPublic toggled

问题描述

"@ Environment(.managedObjectContext)var context"将监视上下文的更改.当我单击按钮以切换isPublic时，我认为它将导致UI刷新，按钮文本将更改，但是为什么呢?

'@Environment(.managedObjectContext) var context' will monitor the changes of context. When I click the button to toggle isPublic, I think it will cause to UI refreshing, Button text will change, But not, WHY?

struct BookInfoView: View {
    @Environment(\.managedObjectContext) var context
    var isPublic: Bool { return book.isPublic }
    
    let book: Book
    
    var body: some View {
        print("refresh"); return
            Group {
                Button(action: onPublicToggled) {
                    Text(isPublic ? "private" : "public")
                }
            }
    }
    
    func onPublicToggled() {
        context.perform {
            book.isPublic.toggle()
            try? context.save()
        }
    }
}

推荐答案

您需要通过 ObservedObject 包装器(如

struct BookInfoView: View {
    @Environment(\.managedObjectContext) var context
    @ObservedObject var book: Book
    
    var body: some View {
        print("refresh"); return
            Group {
                Button(action: onPublicToggled) {
                    Text(book.isPublic ? "private" : "public")
                }
            }
    }
    
    func onPublicToggled() {
        context.perform {
            book.isPublic.toggle()
            try? context.save()
        }
    }
}

注意: @Environment(\.managedObjectContext)var context 与 context 本身有关，而不与CoreData对象有关.

Note: @Environment(\.managedObjectContext) var context relates to context itself, not to your CoreData objects.

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