如何从哈希中删除密钥并在Ruby / Rails中获取剩余的哈希值？ [英] How to remove a key from Hash and get the remaining hash in Ruby/Rails?

问题描述

  {：a => 1，：b => 2} .merge！（{：c => 3}）＃=> {：a => 1，：b => 2，：c => 3} 
  

有没有类似的方法可以从哈希中删除一个键？

这是有效的：

  {：a => 1，：b => 2} .reject！ {| k | k ==：a}＃=> {：b => 2} 
  

但我预计会有这样的内容：

  {：a => 1，：b => 2} .delete！（：a）＃=> {：b => 2} 
  

重要的是返回的值将是剩余的散列值，所以我可以做这样的事情：

  foo（my_hash.reject！{| k | k == my_key}）
  

在一行中。

< Rails有一个除/除！以外的其他内容。方法，该方法返回散列，并删除这些键。如果你已经使用Rails，那么创建你自己的版本是没有意义的。

  class Hash 
＃返回一个散列，其中包含除给定键以外的所有内容。 
＃hash = {a：true，b：false，c：nil} 
＃hash.except（：c）＃=> {a：true，b：false} 
＃hash＃=> {a：true，b：false，c：nil} 
＃
＃这对于一组参数限制一些已知切换的参数非常有用：
＃@ person.update（ （*键）
 dup.except！（*键）
结束
 
＃取代散列没有给定的键。 
＃hash = {a：true，b：false，c：nil} 
＃hash.except！（：c）＃=> {a：true，b：false} 
＃hash＃=> {a：true，b：false} 
 def除了！（*键）
 keys.each {| key | delete（key）} 
 self 
 end 
 end 
  

To add a new pair to Hash I do:

{:a => 1, :b => 2}.merge!({:c => 3})   #=> {:a => 1, :b => 2, :c => 3}

Is there a similar way to delete a key from Hash ?

This works:

{:a => 1, :b => 2}.reject! { |k| k == :a }   #=> {:b => 2}

but I would expect to have something like:

{:a => 1, :b => 2}.delete!(:a)   #=> {:b => 2}

It is important that the returning value will be the remaining hash, so I could do things like:

foo(my_hash.reject! { |k| k == my_key })

in one line.

解决方案

Rails has an except/except! method that returns the hash with those keys removed. If you're already using Rails, there's no sense in creating your own version of this.

class Hash
  # Returns a hash that includes everything but the given keys.
  #   hash = { a: true, b: false, c: nil}
  #   hash.except(:c) # => { a: true, b: false}
  #   hash # => { a: true, b: false, c: nil}
  #
  # This is useful for limiting a set of parameters to everything but a few known toggles:
  #   @person.update(params[:person].except(:admin))
  def except(*keys)
    dup.except!(*keys)
  end

  # Replaces the hash without the given keys.
  #   hash = { a: true, b: false, c: nil}
  #   hash.except!(:c) # => { a: true, b: false}
  #   hash # => { a: true, b: false }
  def except!(*keys)
    keys.each { |key| delete(key) }
    self
  end
end

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