require "delegate"

[0] Fix | Delete

[1] Fix | Delete

# Weak Reference class that allows a referenced object to be

[2] Fix | Delete

# garbage-collected.

[3] Fix | Delete

#

[4] Fix | Delete

# A WeakRef may be used exactly like the object it references.

[5] Fix | Delete

#

[6] Fix | Delete

# Usage:

[7] Fix | Delete

#

[8] Fix | Delete

# foo = Object.new # create a new object instance

[9] Fix | Delete

# p foo.to_s # original's class

[10] Fix | Delete

# foo = WeakRef.new(foo) # reassign foo with WeakRef instance

[11] Fix | Delete

# p foo.to_s # should be same class

[12] Fix | Delete

# GC.start # start the garbage collector

[13] Fix | Delete

# p foo.to_s # should raise exception (recycled)

[14] Fix | Delete

#

[15] Fix | Delete

# == Example

[16] Fix | Delete

#

[17] Fix | Delete

# With help from WeakRef, we can implement our own rudimentary WeakHash class.

[18] Fix | Delete

#

[19] Fix | Delete

# We will call it WeakHash, since it's really just a Hash except all of it's

[20] Fix | Delete

# keys and values can be garbage collected.

[21] Fix | Delete

#

[22] Fix | Delete

# require 'weakref'

[23] Fix | Delete

#

[24] Fix | Delete

# class WeakHash < Hash

[25] Fix | Delete

# def []= key, obj

[26] Fix | Delete

# super WeakRef.new(key), WeakRef.new(obj)

[27] Fix | Delete

# end

[28] Fix | Delete

# end

[29] Fix | Delete

#

[30] Fix | Delete

# This is just a simple implementation, we've opened the Hash class and changed

[31] Fix | Delete

# Hash#store to create a new WeakRef object with +key+ and +obj+ parameters

[32] Fix | Delete

# before passing them as our key-value pair to the hash.

[33] Fix | Delete

#

[34] Fix | Delete

# With this you will have to limit your self to String keys, otherwise you

[35] Fix | Delete

# will get an ArgumentError because WeakRef cannot create a finalizer for a

[36] Fix | Delete

# Symbol. Symbols are immutable and cannot be garbage collected.

[37] Fix | Delete

#

[38] Fix | Delete

# Let's see it in action:

[39] Fix | Delete

#

[40] Fix | Delete

# omg = "lol"

[41] Fix | Delete

# c = WeakHash.new

[42] Fix | Delete

# c['foo'] = "bar"

[43] Fix | Delete

# c['baz'] = Object.new

[44] Fix | Delete

# c['qux'] = omg

[45] Fix | Delete

# puts c.inspect

[46] Fix | Delete

# #=> {"foo"=>"bar", "baz"=>#<Object:0x007f4ddfc6cb48>, "qux"=>"lol"}

[47] Fix | Delete

#

[48] Fix | Delete

# # Now run the garbage collector

[49] Fix | Delete

# GC.start

[50] Fix | Delete

# c['foo'] #=> nil

[51] Fix | Delete

# c['baz'] #=> nil

[52] Fix | Delete

# c['qux'] #=> nil

[53] Fix | Delete

# omg #=> "lol"

[54] Fix | Delete

#

[55] Fix | Delete

# puts c.inspect

[56] Fix | Delete

# #=> WeakRef::RefError: Invalid Reference - probably recycled

[57] Fix | Delete

#

[58] Fix | Delete

# You can see the local variable +omg+ stayed, although its reference in our

[59] Fix | Delete

# hash object was garbage collected, along with the rest of the keys and

[60] Fix | Delete

# values. Also, when we tried to inspect our hash, we got a WeakRef::RefError.

[61] Fix | Delete

# This is because these objects were also garbage collected.

[62] Fix | Delete

[63] Fix | Delete

class WeakRef < Delegator

[64] Fix | Delete

[65] Fix | Delete

##

[66] Fix | Delete

# RefError is raised when a referenced object has been recycled by the

[67] Fix | Delete

# garbage collector

[68] Fix | Delete

[69] Fix | Delete

class RefError < StandardError

[70] Fix | Delete

end

[71] Fix | Delete

[72] Fix | Delete

@@__map = ::ObjectSpace::WeakMap.new

[73] Fix | Delete

[74] Fix | Delete

##

[75] Fix | Delete

# Creates a weak reference to +orig+

[76] Fix | Delete

#

[77] Fix | Delete

# Raises an ArgumentError if the given +orig+ is immutable, such as Symbol,

[78] Fix | Delete

# Fixnum, or Float.

[79] Fix | Delete

[80] Fix | Delete

def initialize(orig)

[81] Fix | Delete

case orig

[82] Fix | Delete

when true, false, nil

[83] Fix | Delete

@delegate_sd_obj = orig

[84] Fix | Delete

else

[85] Fix | Delete

@@__map[self] = orig

[86] Fix | Delete

end

[87] Fix | Delete

super

[88] Fix | Delete

end

[89] Fix | Delete

[90] Fix | Delete

def __getobj__ # :nodoc:

[91] Fix | Delete

@@__map[self] or defined?(@delegate_sd_obj) ? @delegate_sd_obj :

[92] Fix | Delete

Kernel::raise(RefError, "Invalid Reference - probably recycled", Kernel::caller(2))

[93] Fix | Delete

end

[94] Fix | Delete

[95] Fix | Delete

def __setobj__(obj) # :nodoc:

[96] Fix | Delete

end

[97] Fix | Delete

[98] Fix | Delete

##

[99] Fix | Delete

# Returns true if the referenced object is still alive.

[100] Fix | Delete

[101] Fix | Delete

def weakref_alive?

[102] Fix | Delete

@@__map.key?(self) or defined?(@delegate_sd_obj)

[103] Fix | Delete

end

[104] Fix | Delete

end

[105] Fix | Delete

[106] Fix | Delete