Slice a hash to include only the given keys. This is useful for limiting an options hash to valid keys before passing to a method: 

  def search(criteria = {})
    assert_valid_keys(:mass, :velocity, :time)
  end

  search(options.slice(:mass, :velocity, :time))
Methods
Public Instance methods
slice(*keys)

Returns a new hash with only the given keys.

[ show source ]

    # File lib/active_support/core_ext/hash/slice.rb, line 16
16:         def slice(*keys)
17:           allowed = Set.new(respond_to?(:convert_key) ? keys.map { |key| convert_key(key) } : keys)
18:           hash = {}
19:           allowed.each { |k| hash[k] = self[k] if has_key?(k) }
20:           hash
21:         end
slice!(*keys)

Replaces the hash with only the given keys.

[ show source ]

    # File lib/active_support/core_ext/hash/slice.rb, line 24
24:         def slice!(*keys)
25:           replace(slice(*keys))
26:         end