Ruby: Swap out hash key with matching value from other hash

Question

I have these hashes:

hash  = {1 => "popcorn", 2 => "soda"}
other_hash = {1 => "dave", 2 => "linda", 3 => "bobby_third_wheel"}

I would like to replace the id reference with the name associated to the id in the second hash, if there is a record in other_hash that has nothing to match, it should just be dropped in the resulting hash. Like this:

the_one_hash_to_rule_them_all = {"dave" => "popcorn", "linda" => "soda"}

Answer 1

You can easly use this each_with_object method on "primary" hash with names.

other_hash.each_with_object({}) { |(id, name), h| h[name] = hash[id] if hash.key?(id) }
# => {"dave"=>"popcorn", "linda"=>"soda"}

Answer 2

hash.each_with_object({}){|(k,v), res| res[other_hash[k]] = v}
# => {"dave"=>"popcorn", "linda"=>"soda"}

Answer 3

First, an "array-comprehension" with the pattern enumerable.map { expr if condition }.compact and finally an Array#to_h .

h = other_hash.map { |k, v| [v, hash[k]] if hash.has_key?(k) }.compact.to_h
#=> {"dave"=>"popcorn", "linda"=>"soda"}

Also:

h = other_hash.select { |k, v| hash.has_key?(k) }.map { |k, v| [v, hash[k]] }.to_h

Answer 4

hash.map{|k, v| [other_hash[k], v]}.to_h
# => {"dave"=>"popcorn", "linda"=>"soda"}