引言

Nodify有三层结构，编辑器Editor，节点Node和连接组件Connection，上节介绍了节点和编辑器，本节介绍连接组件。连接组件用于保存节点中连接端子的连接关系，并随节点的拖动改变。

1、连接组件

 连接组件存储一个连接关系，包含源和目标

public class ConnectionViewModel
{
    public ConnectorViewModel Source { get; set; }
    public ConnectorViewModel Target { get; set; }
}

2、连接端子

连接端子有它的名称和位置锚点，其中用到一个MVVM工具包http://t.csdnimg.cn/scDXnhttp://t.csdnimg.cn/scDXn我们拖动节点时连接端子需要跟随移动，连接线也应随之改变，所以需要记录其位置锚点，在xaml中会将其绑定到节点的依赖属性Anchor上，此外还有一个连接状态属性

 public partial class ConnectorViewModel : ObservableObject
 {
     public string Title { get; set; }

     [ObservableProperty]
     private Point _anchor;

     [ObservableProperty]
     private bool _isConnected;
 }

3、编辑器

在编辑器中不仅要存储所有节点，还需要存储节点的连接关系

 public ObservableCollection<ConnectionViewModel> Connections { get; } =
     new ObservableCollection<ConnectionViewModel>();

 public partial class EditorViewModel
 {
     public ObservableCollection<NodeViewModel> Nodes { get; set; } =
         new ObservableCollection<NodeViewModel>();
     public ObservableCollection<ConnectionViewModel> Connections { get; } =
         new ObservableCollection<ConnectionViewModel>();

     public EditorViewModel()
     {
         var welcome = new NodeViewModel()
         {
             Title = "Welcome",
             Input = new ObservableCollection<ConnectorViewModel>
             {
                 new ConnectorViewModel { Title = "输入" }
             },
             Output = new ObservableCollection<ConnectorViewModel>
             {
                 new ConnectorViewModel { Title = "输出" }
             },
             Location = new Point(10, 100)
         };
         var nodify = new NodeViewModel
         {
             Title = "To Nodify",
             Input = new ObservableCollection<ConnectorViewModel>
             {
                 new ConnectorViewModel { Title = "In" }
             }
         };
         Nodes.Add(welcome);
         Nodes.Add(nodify);
         Connections.Add(new ConnectionViewModel(welcome.Output[0], nodify.Input[0]));
     }
}

4、xaml绑定

<Grid>
    <nodify:NodifyEditor
        Name="Editor"
        Connections="{Binding Connections}"
        ItemsSource="{Binding Nodes}">
        <nodify:NodifyEditor.DataContext>
            <vm:EditorViewModel />
        </nodify:NodifyEditor.DataContext>
        <nodify:NodifyEditor.ItemTemplate>
            <DataTemplate DataType="{x:Type mod:NodeViewModel}">
                <nodify:Node
                    Header="{Binding Title}"
                    Input="{Binding Input}"
                    Output="{Binding Output}">
                    <nodify:Node.InputConnectorTemplate>
                        <DataTemplate DataType="{x:Type mod:ConnectorViewModel}">
                            <nodify:NodeInput
                                Anchor="{Binding Anchor, Mode=OneWayToSource}"
                                Header="{Binding Title}"
                                IsConnected="{Binding IsConnected}" />
                        </DataTemplate>
                    </nodify:Node.InputConnectorTemplate>
                    <nodify:Node.OutputConnectorTemplate>
                        <DataTemplate DataType="{x:Type mod:ConnectorViewModel}">
                            <nodify:NodeInput
                                Anchor="{Binding Anchor, Mode=OneWayToSource}"
                                Header="{Binding Title}"
                                IsConnected="{Binding IsConnected}" />
                        </DataTemplate>
                    </nodify:Node.OutputConnectorTemplate>
                </nodify:Node>
            </DataTemplate>
        </nodify:NodifyEditor.ItemTemplate>
        <nodify:NodifyEditor.ConnectionTemplate>
            <DataTemplate DataType="{x:Type vm:ConnectionViewModel}">
                <nodify:StepConnection Source="{Binding Source.Anchor}" Target="{Binding Target.Anchor}" />
            </DataTemplate>
        </nodify:NodifyEditor.ConnectionTemplate>

    </nodify:NodifyEditor>
</Grid>