Need ideas to change a key's name of JSON Object on RUBY

source = { "a" => "b", "b" => "bb", "c" => "lol" }
PATTERN = { "a" => "c", "c" => "e" }
source.inject({}) do |new_hash, (k, v)|
  key = PATTERN[k] || k
  new_hash[key] = v
  new_hash
end
#=> { "c" => "b", "b" => "bb", "e" => "lol" }

If you need this functionality frequently, you can extend the Ruby Hash class.

Implementation would vary from ruby version to version, but roughly something like this:

class Hash
  module ClassMethods
    def self.replace_key(old_key, new_key)
     self[new_key] = self[old_key]
     self.delete(old_key)
    end
  end
end

Basically, creating a new key,value pair in the Hash using the new key and old value. Then deleting the original pair.

Note: Operations like this on large hashes are inadvisable from a performance perspective.

If you are serializing ActiveRecord or ActiveModel object, you can overwrite as_json method of the class. Like so:

class Foo < ActiveRecord::Base
  def as_json(options = { })
     super((options.select {|k,v| k.to_s != "a" }).merge("c" => options["a"]))
  end
end