Harshul Pandav Harshul Pandav - 9 days ago 6
YAML Question

Create nested object from YAML to access attributes via method calls in Ruby

I am completely new to ruby.
I have to parse a YAML file to construct an object

YAML File

projects:
- name: Project1
developers:
- name: Dev1
certifications:
- name: cert1
- name: Dev2
certifications:
- name: cert2
- name: Project2
developers:
- name: Dev1
certifications:
- name: cert3
- name: Dev2
certifications:
- name: cert4


I want to create an object from this YAML for which I wrote the following code in Ruby

require 'yaml'
object = YAML.load(File.read('./file.yaml'))


I can successfully access the attributes of this object with []
For e.g.

puts object[projects].first[developers].last[certifications].first[name]
# prints ABC


However, I want to access the attributes via method calls

For e.g.

puts object.projects.first.developers.last.certifications.first.name
# should print ABC


Is there any way to construct such an object whose attributes can be accessed in the (dots) way mentioned above?
I have read about OpenStruct and hashugar.
I also want to avoid usage of third party gems

Answer

If you are just experimenting, there is a quick and dirty way to do this:

class Hash
  def method_missing(name, *args)
    send(:[], name.to_s, *args)
  end
end

I wouldn't use that in production code though, since both method_missing and monkey-patching are usually recipes for trouble down the road.

A better solution is to recursively traverse the data-structure and replace hashes with openstructs.

require 'ostruct'
def to_ostruct(object)
  case object
  when Hash
    OpenStruct.new(Hash[object.map {|k, v| [k, to_ostruct(v)] }])
  when Array
    object.map {|x| to_ostruct(x) }
  else
    object
  end
end

puts to_ostruct(object).projects.first.developers.last.certifications.first.name

Note that there are potentially performance issues with either approach if you are doing them a lot - if your application is time-sensitive make sure you benchmark them! This probably isn't relevant to you though.