Accessing elements of nested hashes in ruby

Question

I'm working a little utility written in ruby that makes extensive use of nested hashes. Currently, I'm checking access to nested hash elements as follows:

structure = { :a => { :b => 'foo' }}

# I want structure[:a][:b]

value = nil

if structure.has_key?(:a) && structure[:a].has_key?(:b) then
  value = structure[:a][:b]
end

Is there a better way to do this? I'd like to be able to say:

value = structure[:a][:b]

And get nil if :a is not a key in structure, etc.

Answer 1

Traditionally, you really had to do something like this:

structure[:a] && structure[:a][:b]

However, Ruby 2.3 added a method Hash#dig that makes this way more graceful:

structure.dig :a, :b # nil if it misses anywhere along the way

There is a gem called ruby_dig that will back-patch this for you.