Setting ruby hash .default to a list [duplicate]

Answer 1

I'm not sure if this is what you want, but you can do this to always return an empty array when a missing hash key is queried.

h = Hash.new { [] }
h[:missing]
   => []

#But, you should never modify the empty array because it isn't stored anywhere
#A new, empty array is returned every time
h[:missing] << 'entry'
h[:missing]
   => []