How to create a deep copy of an object in Ruby?

Deep copy isn't built into vanilla Ruby, but you can hack it by marshalling and unmarshalling the object:

Marshal.load(Marshal.dump(@object))

This isn't perfect though, and won't work for all objects. A more robust method:

class Object  def deep_clone    return @deep_cloning_obj if @deep_cloning    @deep_cloning_obj = clone    @deep_cloning_obj.instance_variables.each do |var|      val = @deep_cloning_obj.instance_variable_get(var)      begin        @deep_cloning = true        val = val.deep_clone      rescue TypeError        next      ensure        @deep_cloning = false      end      @deep_cloning_obj.instance_variable_set(var, val)    end    deep_cloning_obj = @deep_cloning_obj    @deep_cloning_obj = nil    deep_cloning_obj  endend

Source:

http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-list/43424

I've created a native implementation to perform deep clones of ruby objects.

It's approximately 6 to 7 times faster than the Marshal approach.

https://github.com/balmma/ruby-deepclone

Note that this project is not maintained anymore (last commit in 2017, there are reported issues)

Rails has a recursive method named deep_dup that will return a deep copy of an object and, on the contrary of dup and clone, works even on composite objects (array/hash of arrays/hashes).It's as easy as:

def deep_dup  map { |it| it.deep_dup }end