SwiftUI列出空状态视图/修饰符

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空状态视图.下面是一个示例，其中我必须将其包装在 if/else 语句中.有没有更好的选择，还是有办法在 List 上创建一个修饰符，使之成为可能，即 List.emptyView(Text(")).

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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