問題描述

我習慣于在 PHP 中使用多維數組，我可以在其中分配和初始化散列

I am so used to work in PHP with multi-dimensional arrays, where I can assign and initialize a hash by

unset($a); // just to show that there is no variable $a
$a['settings']['system']['memory'] = '1 Gb';
$a['settings']['system']['disk space'] = '100 Gb';

有沒有辦法在 Ruby 中做類似的事情?或者我需要先初始化所有維度，然后再賦值.是否可以定義一個高級哈希來執行我需要的操作?你會怎么做?

Is there a way to do similar thing in Ruby? Or I need to initialize all dimensions first, and then to assign values. Is it possible to define an advanced Hash which will allow to do what I need? How would you do that?

更新

除了Douglas提出的解決方案(見下文)，我還找到了一個該主題的線程，其中 Brian Schr??er 提出了 Hash 類的擴展:

In addition to the solution proposed by Douglas (see below), I have found a thread on the subject, in which Brian Schr??er has proposed an extension for the Hash class:

class AutoHash < Hash
  def initialize(*args)
    super()
    @update, @update_index = args[0][:update], args[0][:update_key] unless args.empty?
  end

  def [](k)
    if self.has_key?k
      super(k)
    else
      AutoHash.new(:update => self, :update_key => k)
    end
  end

  def []=(k, v)
    @update[@update_index] = self if @update and @update_index
    super
  end
end

它可以解決在僅請求項目值時意外創建丟失的哈希項目時的問題，例如a['key'].

It allows to solve the problem when a missing hash item is undesirably created when the item value was only requested, e.g. a['key'].

一些額外的參考資料

1. ruby 哈希自動激活(方面)
2. http://trevoke.net/blog/2009/11/06/auto-vivifying-hashes-in-ruby/
3. http://www.eecs.harvard.edu/~cduan/technical/ruby/ycombinator.shtml

推薦答案

試試這個:

def hash_with_default_hash
    Hash.new { |hash, key| hash[key] = hash_with_default_hash }
end

a = hash_with_default_hash

如果鍵不存在，則塊的結果將用作默認值.在這種情況下，默認值也是一個散列，它使用散列作為其默認值.

If the key doesn't exist, then the result of the block will be used as the default value. In this case, the default value is also a hash which uses hashes as its default values.

這篇關于在 Ruby 中是否可以像在 PHP 中那樣自動初始化多維哈希數組?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！