Converting a hash into a nested hash

Question

This question is the inverse of this question.

Given a hash that has an array for each key like

{
    [:a, :b, :c] => 1,
    [:a, :b, :d] => 2,         


        

Answer 1

For a mixed hash/array nested structure you can use this. (Modified for arrays as well)

def unflatten(h={})
  ret = {}
  h.each do |k,v|
    node = ret
    keys = k.split('.').collect { |x| x.to_i.to_s == x ? x.to_i : x }
    keys.each_cons(2) do |x, next_d|
      if(next_d.is_a? Fixnum)
        node[x] ||= []
        node=node[x]
      else
        node[x] ||={}
        node=node[x]
      end
    end                                                                                                                                                                                                                                                                         
    node[keys[-1]] = v
  end
  ret
end

provided you used the below for flattening. ( dot separate string for key instead of array [split on . if you need] )

def flatten_hash(hash)
  hash.each_with_object({}) do |(k, v), h|
    if v.is_a? Hash
      flatten_hash(v).map do |h_k, h_v|
        h["#{k}.#{h_k}"] = h_v 
      end 
    elsif v.is_a? Array
      flatten_array(v).map do |h_k,h_v|
        h["#{k}.#{h_k}"] = h_v 
      end 
    else
      h[k] = v 
    end 
  end 
end


def flatten_array(array)
  array.each_with_object({}).with_index do |(v,h),i|
    pp v,h,i
    if v.is_a? Hash
      flatten_hash(v).map do |h_k, h_v|
        h["#{i}.#{h_k}"] = h_v 
      end 
    elsif v.is_a? Array
      flatten_array(v).map do |h_k,h_v|
        h["#{i}.#{h_k}"] = h_v 
      end 
    end 
  end 
end