module Enumerable

# => { created_at: 2020-03-09 22:31:47, updated_at: 2020-03-09 22:31:47 }
%i( created_at updated_at ).index_with(Time.now)

for all elements:
If an argument is passed instead of a block, it will be used as the value

# => { title: "hey there", body: "what's up?" }
%i( title body ).index_with { |attr_name| post.public_send(attr_name) }

post = Post.new(title: "hey there", body: "what's up?")

result as the value.
Convert an enumerable to a hash, using the element as the key and the block

def index_with(default = (no_default = true))
  if block_given?
    result = {}
    each { |elem| result[elem] = yield(elem) }
    result
  elsif no_default
    to_enum(:index_with) { size if respond_to?(:size) }
  else
    result = {}
    each { |elem| result[elem] = default }
    result
  end
end