Class: Ref::SoftReference

Inherits:

Reference

• Object
• Reference
• Ref::SoftReference

Defined in:

lib/ref/soft_reference.rb

Overview

A SoftReference represents a reference to an object that is not seen by the tracing phase of the garbage collector. This allows the referenced object to be garbage collected as if nothing is referring to it.

A SoftReference differs from a WeakReference in that the garbage collector is not so eager to reclaim soft references so they should persist longer.

Example usage:

foo = Object.new
ref = Ref::SoftReference.new(foo)
ref.object			# should be foo
ObjectSpace.garbage_collect
ref.object			# should be foo
ObjectSpace.garbage_collect
ObjectSpace.garbage_collect
ref.object			# should be nil

Direct Known Subclasses

Mock::MockSoftReference

Constant Summary

MIN_GC_CYCLES =

Number of garbage collection cycles after an object is used before a reference to it can be reclaimed.

10

@@strong_references =

[{}]

@@gc_flag_set =

false

@@lock =

SafeMonitor.new

@@finalizer =

lambda do |object_id|
  @@lock.synchronize do
    while @@strong_references.size >= MIN_GC_CYCLES do
      @@strong_references.shift
    end
    @@strong_references.push({}) if @@strong_references.size < MIN_GC_CYCLES
    @@gc_flag_set = false
  end
end

Instance Attribute Summary

Attributes inherited from Reference

#referenced_object_id

Instance Method Summary

• #initialize(obj) ⇒ SoftReference constructor

  Create a new soft reference to an object.

• #object ⇒ Object

  Get the referenced object.

Methods inherited from Reference

#inspect

Constructor Details

#initialize(obj) ⇒ SoftReference

Create a new soft reference to an object.

# File 'lib/ref/soft_reference.rb', line 39

def initialize(obj)
  @referenced_object_id = obj.__id__
  @weak_reference = WeakReference.new(obj)
  add_strong_reference(obj)
end

Instance Method Details

#object ⇒ Object

Get the referenced object. If the object has been reclaimed by the garbage collector, then this will return nil.

# File 'lib/ref/soft_reference.rb', line 47

def object
  obj = @weak_reference.object
  # add a temporary strong reference each time the object is referenced.
  add_strong_reference(obj) if obj
  obj
end