Ruby中Ractor.select方法的move布尔标志作用是什么？

我正尝试理解Ruby中Ractor.select方法里move标志的行为，文档对该标志的描述为：

move boolean flag defines whether yielded value should be copied (default) or moved.

这在Rust这类有所有权模型的语言中容易理解，但我想知道在Ruby中这意味着什么。

实验1：数组类型测试 #

我先运行了一段代码测试move标志的效果：

should_move = true

puts "MOVE: #{should_move}"
r1 = Ractor.new do
  data = [{name: "tom"}, {name: "dick"}, {name: "harry"}]
  puts "[INSIDE RACTOR] data value is #{data} and data object id is :#{data[0].object_id}"
  Ractor.yield(data)
  sleep 2
  puts "[INSIDE RACTOR] data value is #{data} and data object id is :#{data[0].object_id}"
end

ractor, value = Ractor.select(r1, move: should_move)

puts "[OUTSIDE RACTOR] value is: #{value} and value[0] object_id is: #{value[0].object_id}"
p ractor

sleep 3

将should_move设为true和false时，输出结果一致：

MOVE: true
main.rb:4: warning: Ractor is experimental, and the behavior may change in future versions of Ruby! Also there are many implementation issues.
[INSIDE RACTOR (before move)] data value is [{:name=>"tom"}, {:name=>"dick"}, {:name=>"harry"}] and data object id is :60
[OUTSIDE RACTOR (after move)] value is: [{:name=>"tom"}, {:name=>"dick"}, {:name=>"harry"}] and value[0] object_id is: 80
#<Ractor:#2 main.rb:4 blocking>
[INSIDE RACTOR (after move)] data value is [{:name=>"tom"}, {:name=>"dick"}, {:name=>"harry"}] and data object id is :60

实验2：整数类型测试 #

之后我将Ractor内的data变量改为整数值：

should_move = true

puts "MOVE: #{should_move}"
r1 = Ractor.new do
  data = 12
  puts "[INSIDE RACTOR] data value is #{data} and data object id is :#{data.object_id}"
  Ractor.yield(data)
  sleep 2
  puts "[INSIDE RACTOR] data value is #{data} and data object id is :#{data.object_id}"
end

ractor, value = Ractor.select(r1, move: should_move)

puts "[OUTSIDE RACTOR] value is: #{value} and value object_id is: #{value.object_id}"
p ractor

sleep 3

此次实验中move标志的状态同样未影响输出：

MOVE: false
main.rb:4: warning: Ractor is experimental, and the behavior may change in future versions of Ruby! Also there are many implementation issues.
[INSIDE RACTOR (before move)] data value is 12 and data object id is :25
[OUTSIDE RACTOR (after move)] value is: 12 and value object_id is: 25
#<Ractor:#2 main.rb:4 blocking>
[INSIDE RACTOR (after move)] data value is 12 and data object id is :25

为什么实验中move标志没体现差异？ #

• 不可变对象的特殊性：Ruby中的小整数属于不可变的共享对象，无论是否开启move，它们的object_id都不会改变，原Ractor也能正常访问——因为不可变对象不存在并发修改风险，Ruby会直接共享而非复制或移动。
• 可变对象的访问限制未触发：在数组实验中，虽然move: true时对象所有权已转移到外部Ractor，但原Ractor只是读取对象值而非修改，所以没有触发错误。如果在Ractor.yield(data)后尝试修改data（比如data[0][:name] = "jerry"），当move: true时会直接抛出Ractor::MovedError，而move: false（默认复制）时则可以正常修改，因为原Ractor持有的是独立副本。

内容的提问来源于stack exchange，提问作者sreedev