vendor/rails/activesupport/lib/active_support/core_ext/hash/slice.rb

   1 module ActiveSupport #:nodoc:
   2   module CoreExtensions #:nodoc:
   3     module Hash #:nodoc:
   4       # Slice a hash to include only the given keys. This is useful for
   5       # limiting an options hash to valid keys before passing to a method:
   6       #
   7       #   def search(criteria = {})
   8       #     assert_valid_keys(:mass, :velocity, :time)
   9       #   end
  10       #
  11       #   search(options.slice(:mass, :velocity, :time))
  12       #
  13       # If you have an array of keys you want to limit to, you should splat them:
  14       #
  15       #   valid_keys = [:mass, :velocity, :time]
  16       #   search(options.slice(*valid_keys))
  17       module Slice
  18         # Returns a new hash with only the given keys.
  19         def slice(*keys)
  20           keys = keys.map! { |key| convert_key(key) } if respond_to?(:convert_key)
  21           hash = self.class.new
  22           keys.each { |k| hash[k] = self[k] if has_key?(k) }
  23           hash
  24         end
  25
  26         # Replaces the hash with only the given keys.
  27         # Returns a hash contained the removed key/value pairs
  28         #   {:a => 1, :b => 2, :c => 3, :d => 4}.slice!(:a, :b) # => {:c => 3, :d =>4}
  29         def slice!(*keys)
  30           keys = keys.map! { |key| convert_key(key) } if respond_to?(:convert_key)
  31           omit = slice(*self.keys - keys)
  32           hash = slice(*keys)
  33           replace(hash)
  34           omit
  35         end
  36       end
  37     end
  38   end
  39 end
  40