class Hash # 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)) 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 # 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} 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 end