Class: Yuzu::Core::Visitor

Inherits:
Object show all
Defined in:
lib/yuzu/core/visitor.rb

Overview

Visitor is a convenience mechanism for traversing a tree structure. To be traversable, objects in the data structure must have the following interface defined:

def children
  return an array of nodes or nil
end

WebsiteBase and Path have this interface, so are traversable. Given a Proc that returns a boolean, we can limit the operation performed by the visitor to a subset of available nodes.

Usage:

filter_for_files_only = proc {|c| c.file?}
v = Visitor.new(filter_for_files_only)
v.traverse(root) do |child|
  # Do something with child.
end

Each node passing the ‘filter_for_files_only` filter will be executed in the given block.

Instance Method Summary collapse

Constructor Details

#initialize(filter = nil) ⇒ Visitor

Create a visitor

Parameters:

  • filter (Proc) (defaults to: nil) —

    A proc that returns true/false given the child object in question



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# File 'lib/yuzu/core/visitor.rb', line 28

def initialize(filter=nil)
  #raise "Visitor must be given a Proc." if not filter.is_a?(Proc)
  @filter = filter.nil? ? proc {|c| true} : filter
end

Instance Method Details

#traverse(container, &block) ⇒ Object 



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# File 'lib/yuzu/core/visitor.rb', line 33

def traverse(container, &block)
  return if container.children.nil?

  container.children.each do |child|
    block.call(child) if @filter.call(child)
    self.traverse(child, &block) if not child.children.nil?
  end
end