Ruby - update hash keys to strip whitespaces

Question

I would like to strip whitespaces from my hash, so if I have

{"my hash key": 12}

I would like to get

{"myhashkey": 12}

I have found some ways to strip from the values, but got a problem to do that on keys. When I tried

 my_hash.each_key{|k| k.gsub!(' ', '')}

I got the error:

RuntimeError: can't modify frozen String

and if use only gsub (without '!') it runs fine, but doesn't work.

So what's the best way to achieve that? Thanks!

Answer 1

Keys in the hashes are frozen (as the error message says,) and hence they cannot be modified inplace. The new hash must be constructed with new keys:

{"my hash key" => 12}.map { |k, v| [k.delete(' '), v] }.to_h
#⇒ {"myhashkey"=>12}

NB! there is a pitfall: you might lose some values!

{"a b c" => 42, "abc" => :foo}.
  map { |k, v| [k.delete(' '), v] }.to_h
#⇒ {"abc"=>:foo}

Answer 2

You could use transform_keys:

my_hash = { 'my hash key': 12 }
#=> {:"my hash key"=>12}

my_hash.transform_keys { |k| k.to_s.delete(' ').to_sym }
#=> {:myhashkey=>12}

The to_s / to_sym conversion is needed because Symbol doesn't implement delete. You can omit it if your keys are actually strings:

my_hash = { 'my hash key' => 12 }
#=> {:"my hash key"=>12}

my_hash.transform_keys { |k| k.delete(' ') }
#=> {:myhashkey=>12}