Question

a = {"rows" => [{"id" => "231-z", "name" => 'jon', "age"=> 27, "state" => 'AL'}, 
                {"id" => "4121-x", "name" => 'ton', "age"=> 37, "state" => 'VA'}
               ]
    }

b = {"rows" => [{"key" => ["xyz","4121-x"], "value" =>{"sum" => 12312, "realage" => 29}}, 
                {"key" => ["xyz","231-z"], "value" =>{"sum" => 1212, "realage" => 33}}
               ]
    }

In hash a, age is incorrect

In hash b, realage is correct. Also in hash b id is the second value in the first array that maps to id of hash a . Those are 4121-x, 231-z correspond to hash a

I want to correct the age in hash a and swap it with the realage of hash b
I can do it in multiple steps, but is it possible to do it in one liner or very short? So finally correct hash a should look like

a = {"rows" => [{"id" => "231-z", "name" => 'jon', "age"=> 33, "state" => 'AL'}, 
                {"id" => "4121-x", "name" => 'ton', "age"=> 29, "state" => 'VA'}
               ]
    }

Answer 1

does this look reasonable?

a['rows'].each_with_index do |ah, i|
  (bh = b['rows'].select {|h| h['key'].last == ah['id'] }.first) &&
    a['rows'][i] = ah.update('age' => bh['value']['realage'])
end

p a

{
    "rows" => [
        [0] {
               "id" => "231-z",
             "name" => "jon",
              "age" => 33,
            "state" => "AL"
        },
        [1] {
               "id" => "4121-x",
             "name" => "ton",
              "age" => 29,
            "state" => "VA"
        }
    ]
}

Please note it will update a only if corresponding id found in b.

Also, the rows order does not matter, nor matter the rows number, it is only important b to have a row with same id as processed row in a

Here is a Working Demo