Class: TreeRb::TreeNodeVisitor

Inherits:
Object
  • Object
show all
Defined in:
lib/tree_rb/core/tree_node_visitor.rb

Overview

More complex TreeNodeVisitor, define a simple dsl

Examples:

TreeNodeVisitor.new do
  on_enter_node do |node|
    puts "hello #{node}"
  end
  on_exit_node do |node|
    puts "bye #{node}"
  end
  on_leaf do |leaf|
    puts "how you do #{leaf}"
  end
end

Instance Method Summary collapse

Constructor Details

#initialize(delegate = nil, &block) ⇒ TreeNodeVisitor

Returns a new instance of TreeNodeVisitor.

Parameters:

  • delegate (Object) (defaults to: nil) 


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# File 'lib/tree_rb/core/tree_node_visitor.rb', line 22

def initialize(delegate = nil, &block)
  @on_enter_tree_node_blocks = []
  @on_exit_tree_node_blocks  = []
  @on_visit_leaf_node_blocks = []
  @stack                     = []
  @root                      = nil
  @delegate                  = delegate
  if block
    instance_eval(&block)
  end
end

Instance Method Details

#cannot_enter_node(tree_node, error) ⇒ Object

called when the tree node is not accessible or an exception is raise when the node is accessed

Parameters:

  • error (Object) 


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# File 'lib/tree_rb/core/tree_node_visitor.rb', line 58

def cannot_enter_node( tree_node, error)
end

#enter_node(tree_node) ⇒ Object

called on tree node at start of the visit i.e. we start to visit the subtree



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# File 'lib/tree_rb/core/tree_node_visitor.rb', line 37

def enter_node(tree_node)
  parent = @stack.last
  if @delegate
    @delegate.enter_node(tree_node) if @delegate.respond_to? :enter_node
  else
    @on_enter_tree_node_blocks.each do |b|
      if b.arity == 1
        b.call(tree_node)
      elsif b.arity == 2
        b.call(tree_node, parent)
      end
    end
  end
  @root = tree_node if @stack.empty?
  @stack.push(tree_node)
end

#exit_node(tree_node) ⇒ Object

called on tree node at end of the visit i.e. oll subtree are visited



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# File 'lib/tree_rb/core/tree_node_visitor.rb', line 64

def exit_node(tree_node)
  parent = @stack.last
  if @delegate
    @delegate.exit_node(tree_node) if @delegate.respond_to? :exit_node
  else
    @on_exit_tree_node_blocks.each do |b|
      if b.arity == 1
        b.call(tree_node)
      elsif b.arity == 2
        b.call(tree_node, parent)
      end
    end
  end
  @stack.pop
end

#on_enter_node(&block) ⇒ Object

add a block to be called when entering into a tree_node



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# File 'lib/tree_rb/core/tree_node_visitor.rb', line 101

def on_enter_node(&block)
  raise 'already defined a delegate' if @delegate
  raise 'block missing' unless block
  @on_enter_tree_node_blocks << block
end

#on_exit_node(&block) ⇒ Object

add a block to be called when exiting from a TreeNode



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# File 'lib/tree_rb/core/tree_node_visitor.rb', line 110

def on_exit_node(&block)
  raise 'already defined a delegate' if @delegate
  raise 'block missing' unless block
  @on_exit_tree_node_blocks << block
end

#on_leaf(&block) ⇒ Object

add a block to be called when visiting a leaf node



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# File 'lib/tree_rb/core/tree_node_visitor.rb', line 119

def on_leaf(&block)
  raise 'already defined a delegate' if @delegate
  raise 'block missing' unless block
  @on_visit_leaf_node_blocks << block
end

#visit_leaf(leaf_node) ⇒ Object

called when visit leaf node



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# File 'lib/tree_rb/core/tree_node_visitor.rb', line 83

def visit_leaf(leaf_node)
  parent = @stack.last
  if @delegate
    @delegate.visit_leaf(leaf_node) if @delegate.respond_to? :visit_leaf
  else
    @on_visit_leaf_node_blocks.each do |b|
      if b.arity == 1
        b.call(leaf_node)
      elsif b.arity == 2
        b.call(leaf_node, parent)
      end
    end
  end
end