Class: Wref

Inherits:
Object
  • Object
show all
Defined in:
lib/wref.rb

Overview

A simple weak-reference framework with mapping. Only handles the referencing of objects.

Examples

user_obj = ob.get(:User, 1) weak_ref = Wref.new(user_obj) user_obj = nil sleep 0.5 GC.start

begin

user_obj = weak_ref.get
print "The user still exists in memory and has ID #{user.id}."

rescue Wref::Recycled

print "The user has been removed from memory."

end

Defined Under Namespace

Classes: Recycled

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(obj) ⇒ Wref

Initializes various variables.



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# File 'lib/wref.rb', line 25

def initialize(obj)
  if RUBY_ENGINE == "jruby"
    @weakref = java.lang.ref.WeakReference.new(obj)
  else
    @id = obj.__id__
    @class_name = obj.class.name.to_sym
    ObjectSpace.define_finalizer(obj, self.method(:destroy))
    
    if obj.respond_to?(:__object_unique_id__)
      @unique_id = obj.__object_unique_id__
    end
  end
end

Instance Attribute Details

#class_name ⇒ Object (readonly)

Returns the classname of the object.



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# File 'lib/wref.rb', line 19

def class_name
  @class_name
end

#id ⇒ Object (readonly)

Returns the object-ID which is used to look up the ObjectSpace (if not running JRuby).



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# File 'lib/wref.rb', line 22

def id
  @id
end

Instance Method Details

#alive? ⇒ Boolean Also known as: weakref_alive?

Returns true if the reference is still alive. print “The object still exists in memory.” if wref.alive?

Returns:

  • (Boolean) 


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# File 'lib/wref.rb', line 89

def alive?
  begin
    self.get
    return true
  rescue Wref::Recycled
    return false
  end
end

#destroy(*args) ⇒ Object

Destroyes most variables on the object, releasing memory and returning ‘Wref::Recycled’ all the time. It takes arguments because it can be called from destructor of the original object. It doesnt use the arguments for anything.



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# File 'lib/wref.rb', line 40

def destroy(*args)
  @id = nil
  @class_name = nil
  @unique_id = nil
  @weakref = nil
end

#get ⇒ Object Also known as: __getobj__

Returns the object that this weak reference holds or raises Wref::Recycled. begin

obj = wref.get
print "Object still exists in memory."

rescue Wref::Recycled

print "Object has been garbage-collected."

end



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# File 'lib/wref.rb', line 54

def get
  begin
    if RUBY_ENGINE == "jruby"
      raise Wref::Recycled if !@weakref
      obj = @weakref.get
      
      if obj == nil
        raise Wref::Recycled
      else
        return obj
      end
    else
      raise Wref::Recycled if !@class_name or !@id
      obj = ObjectSpace._id2ref(@id)
      
      #Some times this class-name will be nil for some reason - knj
      obj_class_name = obj.class.name
      
      if !obj_class_name or @class_name != obj_class_name.to_sym or @id != obj.__id__
        raise Wref::Recycled
      end
      
      if @unique_id
        raise Wref::Recycled if !obj.respond_to?(:__object_unique_id__) or obj.__object_unique_id__ != @unique_id
      end
      
      return obj
    end
  rescue RangeError, TypeError
    raise Wref::Recycled
  end
end