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))

If you have an array of keys you want to limit to, you should splat them:

valid_keys = [:mass, :velocity, :time]
search(options.slice(*valid_keys))
Methods
S
Instance Public methods
slice(*keys)

Returns a new hash with only the given keys.

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

Replaces the hash with only the given keys. Returns a hash contained the removed key/value pairs

{:a => 1, :b => 2, :c => 3, :d => 4}.slice!(:a, :b) # => {:c => 3, :d =>4}
# File activesupport/lib/active_support/core_ext/hash/slice.rb, line 29
def slice!(*keys)
  keys = keys.map! { |key| convert_key(key) } if respond_to?(:convert_key)
  omit = slice(*self.keys - keys)
  hash = slice(*keys)
  replace(hash)
  omit
end