Module: ObjectSpace

Relationships & Source Files
Namespace Children
Classes: WeakMap
Defined in:	gc.c

Overview

The ObjectSpace module contains a number of routines that interact with the garbage collection facility and allow you to traverse all living objects with an iterator.

ObjectSpace also provides support for object finalizers, procs that will be called when a specific object is about to be destroyed by garbage collection.

require 'objspace'

a = "A"
b = "B"

ObjectSpace.define_finalizer(a, proc {|id| puts "Finalizer one on #{id}" })
ObjectSpace.define_finalizer(b, proc {|id| puts "Finalizer two on #{id}" })

produces:

Finalizer two on 537763470
Finalizer one on 537763480

Class Method Summary

._id2ref(object_id) ⇒ Object mod_func

Converts an object id to a reference to the object.
.count_objects([result_hash]) ⇒ Hash mod_func

Counts all objects grouped by type.
.define_finalizer(obj, aProc = proc()) mod_func

Adds aProc as a finalizer, to be called after obj was destroyed.
.each_object([module]) {|obj| ... } ⇒ Integer mod_func

Calls the block once for each living, nonimmediate object in this Ruby process.
.garbage_collect ⇒ nil mod_func

Alias for GC.start.
.undefine_finalizer(obj) mod_func

Removes all finalizers for obj.

Class Method Details

._id2ref(object_id) ⇒ Object (mod_func)

Converts an object id to a reference to the object. May not be called on an object id passed as a parameter to a finalizer.

s = "I am a string"                    #=> "I am a string"
r = ObjectSpace._id2ref(s.object_id)   #=> "I am a string"
r == s                                 #=> true

.count_objects([result_hash]) ⇒ Hash (mod_func)

Counts all objects grouped by type.

It returns a hash, such as:

{
  :TOTAL=>10000,
  :FREE=>3011,
  :T_OBJECT=>6,
  :T_CLASS=>404,
  # ...
}

The contents of the returned hash are implementation specific. It may be changed in future.

The keys starting with :T_ means live objects. For example, :T_ARRAY is the number of arrays. :FREE means object slots which is not used now. :TOTAL means sum of above.

If the optional argument result_hash is given, it is overwritten and returned. This is intended to avoid probe effect.

h = {}
ObjectSpace.count_objects(h)
puts h
# => { :TOTAL=>10000, :T_CLASS=>158280, :T_MODULE=>20672, :T_STRING=>527249 }

This method is only expected to work on C Ruby.

.define_finalizer(obj, aProc = proc()) (mod_func)

Adds aProc as a finalizer, to be called after obj was destroyed. The object ID of the obj will be passed as an argument to aProc. If aProc is a lambda or method, make sure it can be called with a single argument.

.each_object([module]) {|obj| ... } ⇒ Integer (mod_func) .each_object([module]) ⇒ Enumerator

Calls the block once for each living, nonimmediate object in this Ruby process. If module is specified, calls the block for only those classes or modules that match (or are a subclass of) module. Returns the number of objects found. Immediate objects (Fixnums, ::Symbols true, false, and nil) are never returned. In the example below, each_object returns both the numbers we defined and several constants defined in the ::Math module.

If no block is given, an enumerator is returned instead.

a = 102.7
b = 95       # Won't be returned
c = 12345678987654321
count = ObjectSpace.each_object(Numeric) {|x| p x }
puts "Total count: #{count}"

produces:

12345678987654321
102.7
2.71828182845905
3.14159265358979
2.22044604925031e-16
1.7976931348623157e+308
2.2250738585072e-308
Total count: 7

.garbage_collect ⇒ `nil` (mod_func) .garbage_collect(full_mark: true, immediate_sweep: true) ⇒ `nil`

Alias for GC.start.

.undefine_finalizer(obj) (mod_func)

Removes all finalizers for obj.