如何在Ruby中复制散列？ [英] How do I copy a hash in Ruby?

问题描述

我承认我是一个红宝石新手（现在写rake脚本）。在大多数语言中，复制构造函数很容易找到。半小时的搜索没有发现红宝石。我想创建一个散列的副本，以便我可以修改它而不影响原始实例。

I'll admit that I'm a bit of a ruby newbie (writing rake scripts, now). In most languages, copy constructors are easy to find. Half an hour of searching didn't find it in ruby. I want to create a copy of the hash so that I can modify it without affecting the original instance.

一些预期的方法无法按预期工作：

Some expected methods that don't work as intended:

h0 = {  "John"=>"Adams","Thomas"=>"Jefferson","Johny"=>"Appleseed"}
h1=Hash.new(h0)
h2=h1.to_hash

与此同时，我采取了这种不合理的解决方法

In the meantime, I've resorted to this inelegant workaround

def copyhash(inputhash)
  h = Hash.new
  inputhash.each do |pair|
    h.store(pair[0], pair[1])
  end
  return h
end

推荐答案

clone 方法是Ruby的标准内置方法，可以执行浅拷贝：

The clone method is Ruby's standard, built-in way to do a shallow-copy:

irb(main):003:0> h0 = {"John" => "Adams", "Thomas" => "Jefferson"}
=> {"John"=>"Adams", "Thomas"=>"Jefferson"}
irb(main):004:0> h1 = h0.clone
=> {"John"=>"Adams", "Thomas"=>"Jefferson"}
irb(main):005:0> h1["John"] = "Smith"
=> "Smith"
irb(main):006:0> h1
=> {"John"=>"Smith", "Thomas"=>"Jefferson"}
irb(main):007:0> h0
=> {"John"=>"Adams", "Thomas"=>"Jefferson"}

请注意，该行为可能被覆盖：

Note that the behavior may be overridden:

此方法可能具有类特定的行为。如果是这样，该行为将记录在该类的 #initialize_copy 方法下。

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