How to get the first key and value pair from a hash table in Ruby

Question

I'm trying to get the first key and value key from a hash table in ruby. I don't know the key values of the hash because it is passed to the method. I cant find anywhere online how to find the first key/value as a separate hash table. I think hash[0] will just try to find an element with a name 0 it just returns nil when I run the code.

I know I can find the key name and the value and then create a new hash from them but i wonder if there is an easier way to do this so I get a hash right away.

here is my code:

def rps_game_winner(game)  rock_in_hash = game.invert['R'] paper_in_hash = game.invert['P'] scissors_in_hash = game.invert['S']  if(rock_in_hash)       if(paper_in_hash)         return paper_in_hash;       elsif(scissors_in_hash)         return rock_in_hash       end     elsif(paper_in_hash)       if(rock_in_hash)         return paper_in_hash       elsif(scissors_in_hash)         return scissors_in_hash       end     end         key = game.keys[-1]         value = game.values[-1]             winner = {key => value}     return winner      end  game_one = { "Bob" => 'P', "Jim" => 'P' }  puts rps_game_winner(game_one) 

This gets me the correct result the problem is I don't understand why it's -1 instead of zero... And i was hoping there was a better way to get the first key/value pair of a hash table instead of creating new hash table with the key and value you retrieved from the previous table.

Answer 1

You can just do

key, value = hash.first 

or if you prefer:

key = hash.keys[0] value = hash.values[0] 

Then maybe:

new_hash = {key => value} 

Answer 2

There is a shorter answer that does not require you to use extra variables:

h = { "a" => 100, "b" => 200 , "c" => 300, "d" => 400, "e" => 500} Hash[*h.first] #=> {"a" => 100} 

Or if you want to retrieve a key/value at a any single position

Hash[*h.to_a.at(1)] #=> {"b" => 200} 

Or retrieve a key/values from a range of positions:

 Hash[h.to_a[1,3]] #=> {"b"=>200, "c"=>300, "d"=>400}