How to find a hash key containing a matching value

Solution 1:

Ruby 1.9 and greater:

hash.key(value) => key

Ruby 1.8:

You could use hash.index

hsh.index(value) => key

Returns the key for a given value. If not found, returns nil.

h = { "a" => 100, "b" => 200 }
h.index(200) #=> "b"
h.index(999) #=> nil

So to get "orange", you could just use:

clients.key({"client_id" => "2180"})

Solution 2:

You could use Enumerable#select:

clients.select{|key, hash| hash["client_id"] == "2180" }
#=> [["orange", {"client_id"=>"2180"}]]

Note that the result will be an array of all the matching values, where each is an array of the key and value.