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.

visitor = 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.

Constants

NO_ARGS

Attributes

cache[R]

max_args[R]

message[R]

min_args[R]

receiver[R]

Public Class Methods

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

   # File lib/puppet/pops/visitor.rb
16 def initialize(receiver, message, min_args=0, max_args=nil)
17   raise ArgumentError.new("min_args must be >= 0") if min_args < 0
18   raise ArgumentError.new("max_args must be >= min_args or nil") if max_args && max_args < min_args
19 
20   @receiver = receiver
21   @message = message
22   @min_args = min_args
23   @max_args = max_args
24   @cache = Hash.new
25 end

Public Instance Methods

visit(thing, *args) click to toggle source

Visit the configured receiver

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

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

Visit an explicit receiver

   # File lib/puppet/pops/visitor.rb
35 def visit_this(receiver, thing, args)
36   raise "Visitor Error: Too few arguments passed. min = #{@min_args}" unless args.length >= @min_args
37   if @max_args
38     raise "Visitor Error: Too many arguments passed. max = #{@max_args}" unless args.length <= @max_args
39   end
40   method_name = @cache[thing.class]
41   if method_name
42     return receiver.send(method_name, thing, *args)
43   else
44     thing.class.ancestors().each do |ancestor|
45       name = ancestor.name
46       next if name.nil?
47       method_name = :"#{@message}_#{name.split(DOUBLE_COLON).last}"
48       next unless receiver.respond_to?(method_name, true)
49       @cache[thing.class] = method_name
50       return receiver.send(method_name, thing, *args)
51     end
52   end
53   raise "Visitor Error: the configured receiver (#{receiver.class}) can't handle instance of: #{thing.class}"
54 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
81 def visit_this_0(receiver, thing)
82   method_name = @cache[thing.class]
83   if method_name
84     return receiver.send(method_name, thing)
85   end
86   visit_this(receiver, thing, NO_ARGS)
87 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
92 def visit_this_1(receiver, thing, arg)
93   method_name = @cache[thing.class]
94   if method_name
95     return receiver.send(method_name, thing, arg)
96   end
97   visit_this(receiver, thing, [arg])
98 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 the general method)

    # File lib/puppet/pops/visitor.rb
103 def visit_this_2(receiver, thing, arg1, arg2)
104   method_name = @cache[thing.class]
105   if method_name
106     return receiver.send(method_name, thing, arg1, arg2)
107   end
108   visit_this(receiver, thing, [arg1, arg2])
109 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
114 def visit_this_3(receiver, thing, arg1, arg2, arg3)
115   method_name = @cache[thing.class]
116   if method_name
117     return receiver.send(method_name, thing, arg1, arg2, arg3)
118   end
119   visit_this(receiver, thing, [arg1, arg2, arg3])
120 end

visit_this_class(receiver, clazz, args) click to toggle source

Visit an explicit receiver

   # File lib/puppet/pops/visitor.rb
57 def visit_this_class(receiver, clazz, args)
58   raise "Visitor Error: Too few arguments passed. min = #{@min_args}" unless args.length >= @min_args
59   if @max_args
60     raise "Visitor Error: Too many arguments passed. max = #{@max_args}" unless args.length <= @max_args
61   end
62   method_name = @cache[clazz]
63   if method_name
64     return receiver.send(method_name, clazz, *args)
65   else
66     clazz.ancestors().each do |ancestor|
67       name = ancestor.name
68       next if name.nil?
69       method_name = :"#{@message}_#{name.split(DOUBLE_COLON).last}"
70       next unless receiver.respond_to?(method_name, true)
71       @cache[clazz] = method_name
72       return receiver.send(method_name, clazz, *args)
73     end
74   end
75   raise "Visitor Error: the configured receiver (#{receiver.class}) can't handle instance of: #{clazz}"
76 end