ruby - Hash ordering preserved between iterations if not modified?

Question

If I iterate over a hash once, then do so again without modifying the contents, are the keys guaranteed to appear in the same order?

A quick test suggests as much:

> h = {'a' => 1, 'b' => 2, 'c' => 3}
> 100_000.times.map { h.to_s == h.to_s }.all?
=> true

Another question, if the above is allowed, can I iterate through it changing only values, without adding any new keys, and have the ordering of the keys be unchanged?

similar to this python question: Do dicts preserve iteration order if they are not modified?

Unlike the proposed duplicate I'm not interested in whether the elements have a fully specified order, only the restriction that two consecutive iterations without modification provide the same sequence.

Answer 1

在 1.9 之前，枚举哈希的行为不在 ruby​​ 规范中，因此取决于实现——基本上，哈希枚举行为/模式没有被语言定义，实现真的可以做他们想做的任何事情（随机？排序？插入顺序？每次都用不同的方法？什么都行！）

1.9+，哈希枚举由语言指定按插入顺序排列，所以如果你知道你的平台是1.9+，你可以依赖它。

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