ruby-on-rails - 如何从哈希中删除一个键并在 Ruby/Rails 中获取剩余的哈希？

Question

要将新对添加到哈希，我会这样做:

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

有没有类似的方法从哈希中删除一个键？

这个有效:

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

但我希望有类似的东西:

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

重要的是返回值将是剩余的哈希值，所以我可以这样做:

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

一行。

Answer 1

Rails has an except/except! method返回删除了这些键的散列。如果您已经在使用 Rails，那么创建您自己的版本是没有意义的。

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