How to check if children is empty

[clouds56]

I'm writing TreeNode as component like this, and would like to check children.is_empty() (in the example, "root" and "right" has_children, while "left" doesn't has_children.
What shall I fill in todo!()?

fn main() -> Element {
  rsx! {
    TreeNode {
      content: "root",
      TreeNode {
        content: "left",
      }
      TreeNode {
        content: "right",
        div { "leaf" }
      }
    }
  }
}

#[component]
fn TreeNode(content: String, children: Element) -> Element {
  let has_children = todo!();
  ...
}

[ealmloff]

cargo expand is a good tool for this type of question. You should see a template for the empty TreeNode that contains a single placeholder in the dynamic_nodes of the VNode. If you only see placeholders in the template, then the rsx was empty

[clouds56]

After some investigation, I found that only check dynamic_nodes is not sufficient, template.roots also plays an important role here.

TreeNode {
  content: "node1",
  div {} // .template.roots == [Element { tag: "div", namespace: None, attrs: [], children: [] }], .dynamic_nodes == []
}
TreeNode {
  content: "node2",
  div { "2" } // .template.roots == [Element { tag: "div", namespace: None, attrs: [], children: [Text { text: "hello" }], .dynamic_nodes == []
}
TreeNode {
  content: "node3",
  TreeNode { // .template.roots == [Dynamic { id: 0 }], .dynamic_nodes == [Component(VComponent { name: "TreeNode" })]
    content: ""
  }
}
TreeNode {
  content: "node4", // .template.roots == [Dynamic { id: 0 }], .dynamic_nodes == [Placeholder(VPlaceholder)]
}

So the solution might be: (correct me if wrong)

pub trait VNodeExt {
  fn is_empty(&self) -> bool;
}

impl VNodeExt for VNode {
  fn is_empty(&self) -> bool {
    self.template.roots.len() == 1 &&
      matches!(self.template.roots[0], TemplateNode::Dynamic { id: 0 }) &&
      matches!(self.dynamic_nodes[0], DynamicNode::Placeholder(_))
  }
}