红宝石：获取嵌套的哈希值的总和

Question

我有哈希部门

{"Mechnical" => {"boys" => "25", "girls"=>"5"}, "Civil"=> {"boys"=>"18", "girls"=>"12"}} 

我想这样的输出，

{"Mechanical" => "30", "Civil => "30"} 

Answer 1

做如下

# If you are in Ruby 2.1 or greater 
your_hash.map { |k,v| [k, v.reduce(0) { |sum, (_, v)| sum + v.to_i }] }.to_h 
# => {"Mechnical"=>30, "Civil"=>30} 

# below Ruby 2.1 
Hash[your_hash.map { |k,v| [k, v.reduce(0) { |sum, (_, v)| sum + v.to_i }] }] 
# => {"Mechnical"=>30, "Civil"=>30} 

# for all versions 
your_hash.each_with_object({}) do |(k,v), h| 
    h[k] = v.reduce(0) { |sum, (_, v)| sum + v.to_i } 
end 
# => {"Mechnical"=>30, "Civil"=>30} 

Answer 2

h = { "Mechnical" => {"boys" => "25", "girls"=>"5"}, 
     "Civil"=> {"boys"=>"18", "girls"=>"12"} } 

h.map { |k, v| [k, v.values.map(&:to_i).sum] }.to_h 
# => {"Mechnical"=>30, "Civil"=>30} 

或者

Hash[ h.map { |k, v| [k, v.values.map(&:to_i).sum]} ] 
# => {"Mechnical"=>30, "Civil"=>30} 

由于您使用Rails，sum会的工作，其他的合理使用inject(:+)