How do I convert hash keys to method names?

Alternatively, if it’s just a small script it might be more convenient to just extend Hash itself

class Hash
  def method_missing sym,*
    fetch(sym){fetch(sym.to_s){super}}
  end
end

method_missing is a magic method that is called whenever your code tries to call a method that does not exist. Ruby will intercept the failing call at run time and let you handle it so your program can recover gracefully. The implementation above tries to access the hash using the method name as a symbol, the using the method name as a string, and eventually fails with Ruby's built-in method missing error.

NB for a more complex script, where adding this behavior might break other third-party gems, you might alternatively use a module and extend each instance

module H
  def method_missing sym,*
    fetch(sym){fetch(sym.to_s){super}}
  end
end

the = { answer: 42 }
the.extend(H)
the.answer # => 42

and for greater convenience you can even propagate the module down to nested hashes

module H
  def method_missing sym,*
    r = fetch(sym){fetch(sym.to_s){super}}
    Hash === r ? r.extend(H) : r
  end
end 

the = { answer: { is: 42 } }
the.extend(H)
the.answer.is # => 42