class Puppet::Pops::Visitor

A Visitor performs delegation to a given receiver based on the configuration of the Visitor. A new visitor is created with a given receiver, a method prefix, min, and max argument counts. e.g.

vistor = Visitor.new(self, "visit_from", 1, 1)

will make the visitor call “self.visit_from_CLASS(x)” where CLASS is resolved to the given objects class, or one of is ancestors, the first class for which there is an implementation of a method will be selected.

Raises RuntimeError if there are too few or too many arguments, or if the receiver is not configured to handle a given visiting object.

Attributes

cache[R]

max_args[R]

message[R]

min_args[R]

receiver[R]

Public Instance Methods

visit(thing, *args) click to toggle source

Visit the configured receiver

# File lib/puppet/pops/visitor.rb, line 26
def visit(thing, *args)
  visit_this(@receiver, thing, *args)
end

visit_this(receiver, thing, *args) click to toggle source

Visit an explicit receiver

# File lib/puppet/pops/visitor.rb, line 31
def visit_this(receiver, thing, *args)
  raise "Visitor Error: Too few arguments passed. min = #{@min_args}" unless args.length >= @min_args
  if @max_args
    raise "Visitor Error: Too many arguments passed. max = #{@max_args}" unless args.length <= @max_args
  end
  if method_name = @cache[thing.class]
    return receiver.send(method_name, thing, *args)
  else
    thing.class.ancestors().each do |ancestor|
      method_name = :"#{@message}_#{ancestor.name.split(/::/).last}"
      next unless receiver.respond_to?(method_name, true)
      @cache[thing.class] = method_name
      return receiver.send(method_name, thing, *args)
    end
  end
  raise "Visitor Error: the configured receiver (#{receiver.class}) can't handle instance of: #{thing.class}"
end

visit_this_0(receiver, thing) click to toggle source

Visit an explicit receiver with 0 args (This is ~30% faster than calling the general method)

# File lib/puppet/pops/visitor.rb, line 52
def visit_this_0(receiver, thing)
  if method_name = @cache[thing.class]
    return receiver.send(method_name, thing)
  end
  visit_this(receiver, thing)
end

visit_this_1(receiver, thing, arg) click to toggle source

Visit an explicit receiver with 1 args (This is ~30% faster than calling the general method)

# File lib/puppet/pops/visitor.rb, line 62
def visit_this_1(receiver, thing, arg)
  if method_name = @cache[thing.class]
    return receiver.send(method_name, thing, arg)
  end
  visit_this(receiver, thing, arg)
end

visit_this_2(receiver, thing, arg1, arg2) click to toggle source

Visit an explicit receiver with 2 args (This is ~30% faster than calling th general method)

# File lib/puppet/pops/visitor.rb, line 72
def visit_this_2(receiver, thing, arg1, arg2)
  if method_name = @cache[thing.class]
    return receiver.send(method_name, thing, arg1, arg2)
  end
  visit_this(receiver, thing, arg1, arg2)
end

visit_this_3(receiver, thing, arg1, arg2, arg3) click to toggle source

Visit an explicit receiver with 3 args (This is ~30% faster than calling the general method)

# File lib/puppet/pops/visitor.rb, line 82
def visit_this_3(receiver, thing, arg1, arg2, arg3)
  if method_name = @cache[thing.class]
    return receiver.send(method_name, thing, arg1, arg2, arg3)
  end
  visit_this(receiver, thing, arg1, arg2, arg3)
end

Public Class Methods

new(receiver, message, min_args=0, max_args=nil) click to toggle source

# File lib/puppet/pops/visitor.rb, line 14
def initialize(receiver, message, min_args=0, max_args=nil)
  raise ArgumentError.new("min_args must be >= 0") if min_args < 0
  raise ArgumentError.new("max_args must be >= min_args or nil") if max_args && max_args < min_args

  @receiver = receiver
  @message = message
  @min_args = min_args
  @max_args = max_args
  @cache = Hash.new
end