这是
this question的一个想法：在创建对象时,增加一个类变量.当对象被收集时,减少它.如您所见,调用终结器,并且@@ no_foo减少.但是当我稍后查询它时,减量就消失了.似乎价值只会上升,永不下降(如果我创建两个对象,它将显示2).我错过了一些明显的东西吗
class Foo
@@no_foo = 0
def initialize
puts 'creating object'
@@no_foo += 1
ObjectSpace.define_finalizer(self,proc { self.delete })
end
def delete
puts 'deleting object'
@@no_foo # => 1
@@no_foo -= 1
@@no_foo # => 0
end
def self.no_foo
@@no_foo # => 0,1
end
end
Foo.no_foo # => 0
f = Foo.new
f = nil
GC.start
Foo.no_foo # => 1
# >> creating object
# >> deleting object
解决方法
它可以工作,但在最终确定中有循环引用.您的终结器取决于应该收集的对象的绑定.见
this solution.
class Foo
@@no_foo = 0
def initialize
@@no_foo += 1
ObjectSpace.define_finalizer(self,Foo.method(:delete))
end
def self.delete id # also this argument seems to be necessary
@@no_foo -= 1
end
def self.no_foo
@@no_foo
end
end
Foo.no_foo # => 0
1000.times{Foo.new}
Foo.no_foo # => 1000
GC.start
Foo.no_foo # => 0