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

Question

I did some searching found some different methods and posts about creating a deep copy operator.

Is there a quick and easy (built-in) way to deep copy objects in Ruby? The fields are not arrays or hashes.

Working in Ruby 1.9.2.

Answer 1

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   end end

Source:

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

Answer 2

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)