我如何从散列中提取子散列？ [英] How do I extract a sub-hash from a hash?

问题描述

我有一个散列：

  h1 = {：a => ：A，：b => ：B，：c => ：C，：d => ：D} 
  

提取这种子哈希的最佳方法是什么？

  h1.extract_subhash（：b，：d，：e，：f）＃=> {：b => ：B，：d => ：D} 
 h1＃=> {：a => ：A，：c => ：C} 
  

解决方案

提取的元素但h1保持不变：

  h1 = {：a => ：A，：b => ：B，：c => ：C，：d => ：D} 
 h2 = h1.select {| key，value | [：b，：d，：e，：f] .include？（key）}＃=> {：b =>：B，：d =>：D} 
 h1 =散列[h1.to_a  -  h2.to_a]＃=> {：a =>：A，：c =>：C} 
  

以将其修补到Hash类中：

$ p $ $ $ $ $ $ $ $ $ def $ extract

h2 = self.select {| key，value | extract.include？（key）}
self.delete_if {| key，value | extract.include？（key）}
h2
end
end

如果你只是想从哈希中删除指定的元素，使用 delete_if 。

  h1 = {：a => ：A，：b => ：B，：c => ：C，：d => ：D} 
 h1.delete_if {| key，value | [：b，：d，：e，：f] .include？（key）}＃=> {：a =>：A，：c =>：C} 
 h1＃=> {：a =>：A，：c =>：C} 
  

I have a hash:

h1 = {:a => :A, :b => :B, :c => :C, :d => :D}

What is the best way to extract a sub-hash like this?

h1.extract_subhash(:b, :d, :e, :f) # => {:b => :B, :d => :D}
h1 #=> {:a => :A, :c => :C}

解决方案

If you specifically want the method to return the extracted elements but h1 to remain the same:

h1 = {:a => :A, :b => :B, :c => :C, :d => :D}
h2 = h1.select {|key, value| [:b, :d, :e, :f].include?(key) } # => {:b=>:B, :d=>:D} 
h1 = Hash[h1.to_a - h2.to_a] # => {:a=>:A, :c=>:C} 

And if you want to patch that into the Hash class:

class Hash
  def extract_subhash(*extract)
    h2 = self.select{|key, value| extract.include?(key) }
    self.delete_if {|key, value| extract.include?(key) }
    h2
  end
end

If you just want to remove the specified elements from the hash, that is much easier using delete_if.

h1 = {:a => :A, :b => :B, :c => :C, :d => :D}
h1.delete_if {|key, value| [:b, :d, :e, :f].include?(key) } # => {:a=>:A, :c=>:C} 
h1  # => {:a=>:A, :c=>:C} 

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