Rails/ruby make new hash

Hashes can only have unique keys, duplicates aren’t allowed. When you insert a duplicate you overwrite any previously existing key with the same name:

Meditate on this:

foo = {} # => {}
foo['a'] = 1
foo # => {"a"=>1}

foo now is a hash of a single key/value pair. If I try to add another element with the same key I only overwrite the previous value, I don’t add another key/value pair:

foo['a'] = 2
foo # => {"a"=>2}

This is essentially what you’re doing with:

arr.each{|el|
  hash['category'] = el[0];
  hash['subcat'] = el[1];
  hash['detail'] = h[2];
}

To make your code work you’ll need to find different names for the keys for each iteration through the loop.

I can add a different key/value though:

foo['b'] = 3
foo # => {"a"=>2, "b"=>3}

See the documentation or any Ruby hash tutorial for more information.

You can use Array#transpose in combination w/ Array#to_h. If you don’t care if the keys of the hash are strings then you can simply do:

arr.transpose.to_h # => {"category"=>"category1", "subcat"=>"subcat1", "detail"=>"detail1"}

If you need the keys to be symbols then you’ll need to do a little more work:

arr.transpose.to_h.inject({}){|hash, (k,v)| hash[k.to_sym] = v; hash }