当EditMode更改时，SwiftUI如何执行动作? [英] SwiftUI how to perform action when EditMode changes?

问题描述

我想在EditMode更改时执行一个操作.

I'd like to perform an action when the EditMode changes.

具体地说，在编辑模式下，用户可以选择一些要删除的项目.他通常随后会按下垃圾桶按钮.但是他也可以按完成".当他以后再次按Edit时，仍会选择以前选择的项目.我希望清除所有物品.

Specifically, in edit mode, the user can select some items to delete. He normally presses the trash button afterwards. But he may also press Done. When he later presses Edit again, the items that were selected previously are still selected. I would like all items to be cleared.

struct ContentView: View {
    @State var isEditMode: EditMode = .inactive
    @State var selection = Set<UUID>()
    var items = [Item(), Item(), Item(), Item(), Item()]

    var body: some View {
        NavigationView {
            List(selection: $selection) {
                ForEach(items) { item in
                    Text(item.title)
                }
            }
            .navigationBarTitle(Text("Demo"))
            .navigationBarItems(
                leading: EditButton(),
                trailing: addDelButton
            )
            .environment(\.editMode, self.$isEditMode)
        }
    }

    private var addDelButton: some View {
        if isEditMode == .inactive {
            return Button(action: reset) {
                Image(systemName: "plus")
            }
        } else {
            return Button(action: reset) {
                Image(systemName: "trash")
            }
        }
    }

    private func reset() {
        selection = Set<UUID>()
    }
}

物品的定义:

struct Item: Identifiable {
    let id = UUID()
    let title: String

    static var i = 0
    init() {
        self.title = "\(Item.i)"
        Item.i += 1
    }
}

推荐答案

@Casper为我指明了正确的方向.这是我想出的.该解决方案用一块石头抓到两只鸟:

@Casper pointed me in the right direction. Here is what I came up with. This solution catches 2 birds with one stone:

1. 在切换editMode时，整个视图会重新绘制
2. 激活/停用editMode后可以执行特定操作

希望这对其他人有帮助.

Hopes this helps someone else.

struct ContentView: View {
    @State var editMode: EditMode = .inactive
    @State var selection = Set<UUID>()
    @State var items = [Item(), Item(), Item()]

    var body: some View {
        NavigationView {
            List(selection: $selection) {
                ForEach(items) { item in
                    Text(item.title)
                }
            }
            .navigationBarTitle(Text("Demo"))
            .navigationBarItems(
                leading: editButton,
                trailing: addDelButton
            )
            .environment(\.editMode, self.$editMode)
        }
    }

    private var editButton: some View {
        Button(action: {
            self.editMode.toggle()
            self.selection = Set<UUID>()
        }) {
            Text(self.editMode.title)
        }
    }

    private var addDelButton: some View {
        if editMode == .inactive {
            return Button(action: addItem) {
                Image(systemName: "plus")
            }
        } else {
            return Button(action: deleteItems) {
                Image(systemName: "trash")
            }
        }
    }

    private func addItem() {
        items.append(Item())
    }

    private func deleteItems() {
        for id in selection {
            if let index = items.lastIndex(where: { $0.id == id }) {
                items.remove(at: index)
            }
        }
        selection = Set<UUID>()
    }
}

extension EditMode {
    var title: String {
        self == .active ? "Done" : "Edit"
    }

    mutating func toggle() {
        self = self == .active ? .inactive : .active
    }
}

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