How to change Hash values?

Question

I\'d like to replace each value in a hash with value.some_method.

For example, for given a simple hash:

{\"a\" => \"b\",         


        

Answer 1

You can collect the values, and convert it from Array to Hash again.

Like this:

config = Hash[ config.collect {|k,v| [k, v.upcase] } ]

Answer 2

This will do it:

my_hash.each_with_object({}) { |(key, value), hash| hash[key] = value.upcase }

As opposed to inject the advantage is that you are in no need to return the hash again inside the block.

Answer 3

Rails-specific

In case someone only needs to call to_s method to each of the values and is not using Rails 4.2 ( which includes transform_values method link), you can do the following:

original_hash = { :a => 'a', :b => BigDecimal('23.4') }
#=> {:a=>"a", :b=>#<BigDecimal:5c03a00,'0.234E2',18(18)>}
JSON(original_hash.to_json)
#=> {"a"=>"a", "b"=>"23.4"}

Note: The use of 'json' library is required.

Note 2: This will turn keys into strings as well

Answer 4

You may want to go a step further and do this on a nested hash. Certainly this happens a fair amount with Rails projects.

Here's some code to ensure a params hash is in UTF-8:

  def convert_hash hash
    hash.inject({}) do |h,(k,v)|
      if v.kind_of? String
        h[k] = to_utf8(v) 
      else
        h[k] = convert_hash(v)
      end
      h
    end      
  end    

  # Iconv UTF-8 helper
  # Converts strings into valid UTF-8
  #
  # @param [String] untrusted_string the string to convert to UTF-8
  # @return [String] your string in UTF-8
  def to_utf8 untrusted_string=""
    ic = Iconv.new('UTF-8//IGNORE', 'UTF-8')
    ic.iconv(untrusted_string + ' ')[0..-2]
  end  

Answer 5

my_hash.each { |k, v| my_hash[k] = v.upcase } 

or, if you'd prefer to do it non-destructively, and return a new hash instead of modifying my_hash:

a_new_hash = my_hash.inject({}) { |h, (k, v)| h[k] = v.upcase; h } 

This last version has the added benefit that you could transform the keys too.

Answer 6

new_hash = old_hash.merge(old_hash) do |_key, value, _value|
             value.upcase
           end

# old_hash = {"a" => "b", "c" => "d"}
# new_hash = {"a" => "B", "c" => "D"}