SwiftUI 列表空状态视图/修改器

问题描述

我想知道当列表的数据源为空时如何在列表中提供一个空的状态视图.下面是一个示例，我必须将它包装在 if/else 语句中.有没有更好的替代方法，或者有没有办法在 List 上创建修饰符，这将使这成为可能，即 List.emptyView(Text("No data available...")).

I was wondering how to provide an empty state view in a list when the data source of the list is empty. Below is an example, where I have to wrap it in an if/else statement. Is there a better alternative for this, or is there a way to create a modifier on a List that'll make this possible i.e. List.emptyView(Text("No data available...")).

import SwiftUI

struct EmptyListExample: View {

    var objects: [Int]

    var body: some View {
        VStack {
            if objects.isEmpty {
                Text("Oops, loos like there's no data...")
            } else {
                List(objects, id: .self) { obj in
                    Text("(obj)")
                }
            }
        }
    }

}

struct EmptyListExample_Previews: PreviewProvider {

    static var previews: some View {
        EmptyListExample(objects: [])
    }

}

推荐答案

解决方案之一是使用@ViewBuilder:

struct EmptyListExample: View {
    var objects: [Int]

    var body: some View {
        listView
    }

    @ViewBuilder
    var listView: some View {
        if objects.isEmpty {
            emptyListView
        } else {
            objectsListView
        }
    }

    var emptyListView: some View {
        Text("Oops, loos like there's no data...")
    }

    var objectsListView: some View {
        List(objects, id: .self) { obj in
            Text("(obj)")
        }
    }
}

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