class Prism::Dispatcher

The dispatcher class fires events for nodes that are found while walking an AST to all registered listeners. It’s useful for performing different types of analysis on the AST while only having to walk the tree once.

To use the dispatcher, you would first instantiate it and register listeners for the events you’re interested in:

class OctalListener
  def on_integer_node_enter(node)
    if node.octal? && !node.slice.start_with?("0o")
      warn("Octal integers should be written with the 0o prefix")
    end
  end
end

listener = OctalListener.new
dispatcher = Prism::Dispatcher.new
dispatcher.register(listener, :on_integer_node_enter)

Then, you can walk any number of trees and dispatch events to the listeners:

result = Prism.parse("001 + 002 + 003")
dispatcher.dispatch(result.value)

Optionally, you can also use dispatch_once to dispatch enter and leave events for a single node without recursing further down the tree. This can be useful in circumstances where you want to reuse the listeners you already have registers but want to stop walking the tree at a certain point.

integer = result.value.statements.body.first.receiver.receiver
dispatcher.dispatch_once(integer)

Attributes

listeners [R]

attr_reader listeners: Hash[Symbol, Array]

Public Class Methods

new ()

Source

# File lib/prism/dispatcher.rb, line 50
def initialize
  @listeners = {}
end

Initialize a new dispatcher.

Public Instance Methods

dispatch_once (node)

Source

# File lib/prism/dispatcher.rb, line 74
def dispatch_once(node)
  node.accept(DispatchOnce.new(listeners))
end

Dispatches a single event for node to all registered listeners.

Source

# File lib/prism/dispatcher.rb, line 55
def register(listener, *events)
  register_events(listener, events)
end

register_public_methods (listener)

Source

# File lib/prism/dispatcher.rb, line 61
def register_public_methods(listener)
  register_events(listener, listener.public_methods(false).grep(/\Aon_.+_(?:enter|leave)\z/))
end