like in php:
$input = [
'a' => 'A',
'b' => 'B',
'cdef' => [
'c' => 'C',
'd' => 'D',
'ef' => [
'e' => 'E',
'f' => 'F'
]
]
]
input = Hash.new
input['a'] = A
input['b'] = 'B'
input['cdef']['c'] = 'C'
input['cdef']['d'] = 'D'
input['cdef']['ef']['e'] = 'E'
input['cdef']['ef']['f'] = 'F'
input['cdef']['c'] = 'C'
[]=' for nil:NilClass
To fix your error, you need to initialize an empty hash before assigning a key-value pair.
input = Hash.new
input['a'] = 'A' #=> {"a"=>"A"}
input['b'] = 'B' #=> {"a"=>"A", "b"=>"B"}
input['cdef'] = {} #=> {"a"=>"A", "b"=>"B", "cdef"=>{}}
input['cdef']['c'] = 'C' #=> {"a"=>"A", "b"=>"B", "cdef"=>{"c"=>"C"}}
input['cdef']['d'] = 'D' #=> {"a"=>"A", "b"=>"B", "cdef"=>{"c"=>"C", "d"=>"D"}}
input['cdef']['ef'] = {} #=> {"a"=>"A", "b"=>"B", "cdef"=>{"c"=>"C", "d"=>"D", "ef"=>{}}}
input['cdef']['ef']['e'] = 'E' #=> {"a"=>"A", "b"=>"B", "cdef"=>{"c"=>"C", "d"=>"D", "ef"=>{"e"=>"E"}}}
input['cdef']['ef']['f'] = 'F' #=> {"a"=>"A", "b"=>"B", "cdef"=>{"c"=>"C", "d"=>"D", "ef"=>{"e"=>"E", "f"=>"F"}}}