How to assign hash['a']['b']= 'c' if hash['a'] doesn't exist?

Question

Is there any way simpler than

if hash.key?(\'a\')
  hash[\'a\'][\'b\'] = \'c\' 
else  
  hash[\'a\'] = {}
  hash[\'a\'][\'b\'] = \'c\' 
end

Answer 1

a simple one, but hash should be a valid hash object

(hash["a"] ||= {})['b'] = "c"