Is it a good idea to use method_missing on nil in ruby

Question

In ruby I'm tired of constantly checking if an object has all necessary properties and sub-properties before using them like

if (obj && obj[:a] && obj[:a][:b] && obj[:a][:b][:c] && obj[:a][:b][:c] > 0)
    # do something useful
end

Is it a good idea to avoid this by defining method_missing on NilClass to return nil?

class NilClass
    def method_missing(method_name, *args, &block)
        nil
    end
end

This way with properly written comparisons I can use default values to handle everything.
I can even compare to other expressions like

if (obj[:a][:b][:c] > 0)
    # do something useful
else
    # default behaviour if obj[:a][:b][:c] <= 0 or obj[:a][:b][:c] is undefined
end

In exceptional cases I can always manually check for nil.

What can get broken?

Answer 1

Using Hash.fetch would allow you to return false if it doesn't exist and short circuit that conditional. http://ruby-doc.org/core-1.9.3/Hash.html#method-i-fetch

if obj.fetch(:a, {}).fetch(:b, {}).fetch(:c, false)
  #useful stuff
end

And as was mentioned in the comments if you really didn't want to check if this object was a hash not you could do (obj||{}).fetch(:a, {}).fetch(:b, {}).fetch(:c, false)