How to avoid NoMethodError for missing elements in nested hashes, without repeated nil checks?

Question

I'm looking for a good way to avoid checking for nil at each level in deeply nested hashes. For example:

name = params[:company][:owner][:name] if params[:company] && params[:company][:owner] && params[:company][:owner][:name]

This requires three checks, and makes for very ugly code. Any way to get around this?

Answer 1

Ruby 2.3.0 introduced a method called dig on both Hash and Array.

name = params.dig(:company, :owner, :name)

It returns nil if the key is missing at any level.

If you are using a version of Ruby older than 2.3, you can install a gem such as ruby_dig or hash_dig_and_collect, or implement the functionality yourself:

module RubyDig
  def dig(key, *rest)
    if value = (self[key] rescue nil)
      if rest.empty?
        value
      elsif value.respond_to?(:dig)
        value.dig(*rest)
      end
    end
  end
end

if RUBY_VERSION < '2.3'
  Array.send(:include, RubyDig)
  Hash.send(:include, RubyDig)
end