Trait datafusion_common::tree_node::TreeNodeVisitor

pub trait TreeNodeVisitor: Sized {
    type Node: TreeNode;

    // Provided methods
    fn f_down(&mut self, _node: &Self::Node) -> Result<TreeNodeRecursion> { ... }
    fn f_up(&mut self, _node: &Self::Node) -> Result<TreeNodeRecursion> { ... }
}

A Visitor for recursively inspecting TreeNodes via TreeNode::visit.

See TreeNode for more details on available APIs

When passed to TreeNode::visit, TreeNodeVisitor::f_down and TreeNodeVisitor::f_up are invoked recursively on the tree. See TreeNodeRecursion for more details on controlling the traversal.

Return Value

The returns value of f_up and f_down specifies how the tree walk should proceed. See TreeNodeRecursion for details. If an Err is returned, the recursion stops immediately.

Note: If using the default implementations of TreeNodeVisitor::f_up or TreeNodeVisitor::f_down that do nothing, consider using TreeNode::apply instead.

See Also:

• TreeNode::rewrite to rewrite owned TreeNodes

Required Associated Types

type Node: TreeNode

The node type which is visitable.

Provided Methods

fn f_down(&mut self, _node: &Self::Node) -> Result<TreeNodeRecursion>

Invoked while traversing down the tree, before any children are visited. Default implementation continues the recursion.

fn f_up(&mut self, _node: &Self::Node) -> Result<TreeNodeRecursion>

Invoked while traversing up the tree after children are visited. Default implementation continues the recursion.

Object Safety

This trait is not object safe.

Implementors