Conteggio valori hash in Ruby

Question

Ho un array di hash in Ruby che assomiglia a questo:

domains = [ 
    { "country" => "Germany"}, 
    {"country" => "United Kingdom"}, 
    {"country" => "Hungary"}, 
    {"country" => "United States"}, 
    {"country" => "France"}, 
    {"country" => "Germany"}, 
    {"country" => "Slovakia"}, 
    {"country" => "Hungary"}, 
    {"country" => "United States"}, 
    {"country" => "Norway"}, 
    {"country" => "Germany"}, 
    {"country" => "United Kingdom"}, 
    {"country" => "Hungary"}, 
    {"country" => "United States"}, 
    {"country" => "Norway"} 
] 

Da questo array di hash Voglio creare un nuovo hash simile a questa:

counted = { 
    "Germany" => "3", 
    "United Kingdom" => "United Kingdom", 
    "Hungary" => "3", 
    "United States" => "4", 
    "France" => "1" 
} 

C'è un modo semplice per farlo usando Ruby 1.9?

Answer 1

Che ne dici di questo?

counted = Hash.new(0) 
domains.each { |h| counted[h["country"]] += 1 } 
counted = Hash[counted.map {|k,v| [k,v.to_s] }] 

Answer 2

domains.each_with_object(Hash.new{|h,k|h[k]='0'}) do |h,res| 
    res[h['country']].succ! 
end 
=> {"Germany"=>"3", 
"United Kingdom"=>"2", 
"Hungary"=>"3", 
"United States"=>"3", 
"France"=>"1", 
"Slovakia"=>"1", 
"Norway"=>"2"}