Question

以下代码不起作用：

let sortDescriptor = NSSortDescriptor(key: "name", ascending: true, selector:"caseInsensitiveCompare")

并给出以下错误： 'NSInvalidArgumentException'，原因：'不支持的NSSortDescriptor选择器：caseInsensitiveCompare'

似乎在Objective-C中工作正常。关于为什么会出现这种情况的任何想法？

编辑：使用Core Data / SQLite似乎无法做到这一点。在这种情况下，获取数组并在之后的代码中对它进行排序是最好的选择吗？

Answer 1

Swift 3 - 5.0语法

public sealed partial class MainPage : Page
{
    public List<String> List;
    public List<String> List2;
    private object PreviousFocusItem;
    public MainPage()
    {
        this.InitializeComponent();
    }

    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        List = new List<string> { "data1_GridView1", "data2_GridView1", "data3_GridView1" };
        List2 = new List<string> { "data1_GridView2", "data2_GridView2", "data3_GridView2" };
        myGridView.ItemsSource = List;
        myGridView2.ItemsSource = List2;
        rootGrid.GotFocus += Grid_GotFocus;
        rootGrid.LostFocus += Grid_LostFocus;
        base.OnNavigatedTo(e);
    }

    private void Grid_LostFocus(object sender, RoutedEventArgs e)
    {
        PreviousFocusItem = e.OriginalSource;
    }

    private void Grid_GotFocus(object sender, RoutedEventArgs e)
    {
        //get the previous focus Element and current focus Element.
        var previous = PreviousFocusItem as UIElement;
        var current = e.OriginalSource as UIElement;

        //got focus logic
        if ((!IsElementInsideGridView(myGridView, previous)) &&IsElementInsideGridView(myGridView,current))
        {
            //gridView got focus as a whole, put your codes here:
            output.Text += "Got Focus+1 \n";
        }

        //lost focus logic
        if ((!IsElementInsideGridView(myGridView, current)) &&(IsElementInsideGridView(myGridView,previous)) )
        {
            //gridView lost focus as a whole, put your codes here:
            output.Text += "Lost Focus+1 \n";
        }
    }

    private bool IsElementInsideGridView(GridView gridView,UIElement element)
    {
        Point topLeft = gridView.TransformToVisual(this).TransformPoint(new Point());
        Rect rectBounds = new Rect(topLeft.X, topLeft.Y, gridView.ActualWidth, gridView.ActualHeight);
        IEnumerable<UIElement> hits = VisualTreeHelper.FindElementsInHostCoordinates(rectBounds, element);
        if (hits == null || hits.Count() == 0)
        {
            return false;
        }
        else
        {
            return true;
        }
    }
}

Answer 2

选择器为...，带冒号，您可以将其与Core Data一起使用。

冒号就在那里，因为该方法（它是caseInsensitiveCompare:的实例方法）接受一个参数（要与之比较的字符串）。

作为可与Core Data和SQLite一起使用的排序选择器列表商店可以找到 核心数据编程指南中的Persistent Store Types and Behaviors。

Answer 3

Swift 5，SwiftUI语法

self._contacts = FetchRequest(
            entity: Contact.entity(),
            sortDescriptors: [
                NSSortDescriptor(key: "name", ascending: true, selector: #selector(NSString.caseInsensitiveCompare(_:)))
            ],
            predicate: predicate
        )

案例不敏感与核心数据和Swift的比较

3 个答案: