Class: Ferret::Utils::WeakKeyHash

Inherits:
Monitor
  • Object
show all
Defined in:
lib/ferret/utils/weak_key_hash.rb

Overview

This class implements a weak key hash. ie all keys that are stored in this hash can still be garbage collected, and if they are garbage collected then the key and it’s corresponding value will be deleted from the hash.

eg.
name = "david"
last_names = WeakKeyHash.new()
last_names[name] = "balmain"
puts last_names["david"]  #=>"balmain"
GC.start
puts last_names["david"]  #=>"balmain"
name = nil
GC.start
# the name "david" will now have been garbage collected so it should
# have been removed from the hash
puts last_names["david"]  #=>nil

WeakKeyHash subclasses Monitor so it can be synchronized on.

NOTE

Unfortunately the ruby garbage collector is not always predictable so your results may differ but each key should eventually be freed when all other references have been removed and the garbage collector is ready.

Instance Method Summary collapse

Constructor Details

#initialize ⇒ WeakKeyHash

Create a new WeakKeyHash.



30
31
32
33
34
 
# File 'lib/ferret/utils/weak_key_hash.rb', line 30

def initialize
  super()
  @hash = {}
  @deleter = lambda{|id| @hash.delete(id)}
end

Instance Method Details

#[](key) ⇒ Object

Get the value for the key



43
44
45
 
# File 'lib/ferret/utils/weak_key_hash.rb', line 43

def [](key)
  return @hash[key.object_id]
end

#[]=(key, value) ⇒ Object

Set the value for the key just like a Hash



37
38
39
40
 
# File 'lib/ferret/utils/weak_key_hash.rb', line 37

def []=(key, value)
  ObjectSpace.define_finalizer(key, @deleter)
  @hash[key.object_id] = value
end

#size ⇒ Object

Return the number of elements in the Hash



48
49
50
 
# File 'lib/ferret/utils/weak_key_hash.rb', line 48

def size
  @hash.size
end

#to_s ⇒ Object

Print a string representation the WeakKeyHash



53
54
55
56
57
 
# File 'lib/ferret/utils/weak_key_hash.rb', line 53

def to_s
  buffer = ""
  @hash.each_pair {|key, value| buffer << "<#{ObjectSpace._id2ref(key)}=>#{value}>"}
  return buffer
end