Krogenth Comments - Answer Overflow

Krogenth

•Created by Krogenth on 8/17/2023 in #help

❔ Avalonia nested ItemsRepeater datatemplates

Well it took a bit of thinking, but the proper approach is a TreeView, with a selector for the TreeDataTemplates. Something like the following should work, where some inheriting objects have children, while others do not:

namespace Types;

public interface BaseInterface
{
  ...
};

// define objects
public class InheritingObjectType : BaseInterface
{
  ...
  public List<BaseInterface> NestedObjects {get;}
};

public class OtherInheritingObjectType : BaseInterface
{
  ...
};
// other implementing classes

namespace Types;

public interface BaseInterface
{
  ...
};

// define objects
public class InheritingObjectType : BaseInterface
{
  ...
  public List<BaseInterface> NestedObjects {get;}
};

public class OtherInheritingObjectType : BaseInterface
{
  ...
};
// other implementing classes

namespace viewmodels;

public class ObjectsViewModel
{
  // collection to feed TreeView
  public ObservableCollection<BaseInterface> Items {get;}
};

namespace viewmodels;

public class ObjectsViewModel
{
  // collection to feed TreeView
  public ObservableCollection<BaseInterface> Items {get;}
};

// tree data template selector
public class SomeSelector : ITreeDataTemplate
{
  [Content]
  public Dictionary<string, IDataTemplate> Templates { get; private set; } = new();

  public InstancedBinding ItemsSelector(object item)
  {
    if (item is BaseInterface obj)
    {
      return ((TreeDataTemplate)Templates[obj.GetType().Name]).ItemsSelector(item);
    }
    else
    {
      return null;
    }
  }

  public IControl Build(object data) =>
    Templates[data.GetType().Name].Build(data);

  public bool Match(object data)
    => data is BaseInterface && Templates.ContainsKey(data.GetType().Name);
}

// tree data template selector
public class SomeSelector : ITreeDataTemplate
{
  [Content]
  public Dictionary<string, IDataTemplate> Templates { get; private set; } = new();

  public InstancedBinding ItemsSelector(object item)
  {
    if (item is BaseInterface obj)
    {
      return ((TreeDataTemplate)Templates[obj.GetType().Name]).ItemsSelector(item);
    }
    else
    {
      return null;
    }
  }

  public IControl Build(object data) =>
    Templates[data.GetType().Name].Build(data);

  public bool Match(object data)
    => data is BaseInterface && Templates.ContainsKey(data.GetType().Name);
}

<TreeView Items="{Binding Items}">
  <TreeView.DataTemplates>
    <selectors:SomeSelector>
      <TreeDataTemplate x:Key="InheritingObjectType"
                        DataType="{x:Type types:InheritingObjectType}"
                        ItemsSource="{Binding NestedObjects}">
        <!-- whatever needs rendered -->
      </TreeDataTemplate>
      <TreeDataTemplate x:Key="OtherInheritingObjectType"
                        DataType="{x:Type types:OtherInheritingObjectType}">
        <!-- whatever needs rendered -->
      </TreeDataTemplate>
      <!-- other datatemplates -->
    </selectors:MapOpcodeSelector>
  </TreeView.DataTemplates>
</TreeView>

<TreeView Items="{Binding Items}">
  <TreeView.DataTemplates>
    <selectors:SomeSelector>
      <TreeDataTemplate x:Key="InheritingObjectType"
                        DataType="{x:Type types:InheritingObjectType}"
                        ItemsSource="{Binding NestedObjects}">
        <!-- whatever needs rendered -->
      </TreeDataTemplate>
      <TreeDataTemplate x:Key="OtherInheritingObjectType"
                        DataType="{x:Type types:OtherInheritingObjectType}">
        <!-- whatever needs rendered -->
      </TreeDataTemplate>
      <!-- other datatemplates -->
    </selectors:MapOpcodeSelector>
  </TreeView.DataTemplates>
</TreeView>

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