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Descendants

A descendant provider tells Reactor that one entity exposes other entities. Presenters traverse the relationship while each child's definition controls its rendering.

The core relationship​

Start with DescendantEntityProviderComponent. It identifies the descendant definition and synchronously generates the current descendants for a parent:

this.registerComponent(
  new DescendantEntityProviderComponent<TodoModel, NoteModel>({
    descendantType: TodoEntities.NOTE,
    generateOptions: (todo) => ({
      descendants: todo.notes,
      category: {
        label: 'Notes',
        openDefault: true
      }
    })
  })
);

Return null when the relationship should not appear for a particular parent. Omit category to place descendants directly beneath the parent, or provide category tree properties to group them under a node.

This base component is enough when the descendants are already available. Tree and card presenters resolve each child through the definition named by descendantType.

Loading and refresh behavior​

DescendantLoadingEntityProviderComponent extends the base relationship. Its generated options may additionally provide refreshDescendants and loading:

this.registerComponent(
  new DescendantLoadingEntityProviderComponent<TodoModel, NoteModel>({
    descendantType: TodoEntities.NOTE,
    generateOptions: (todo) => ({
      descendants: todo.notes,
      loading: () => todo.notesLoading,
      refreshDescendants: () => this.todoStore.loadNotes(todo),
      category: { label: 'Notes' }
    })
  })
);

Use this derivative when opening or revealing a tree node should refresh its children. It adds loading feedback, prevents overlapping refreshes, and surfaces refresh errors on the tree node.

Lazy tree presenters decide when descendants are traversed. Cached tree presenters can preserve generated nodes across refreshes; those presenter choices are separate from the relationship itself.