Ruby Memoization

class User < ActiveRecord::Base
  def twitter_followers
    # assuming twitter_user.followers makes a network call
    @twitter_followers ||= twitter_user.followers
  end
end

# @twitter_followers = @twitter_followers || twitter_user.followers

For multiline

class User < ActiveRecord::Base
  def main_address
    @main_address ||= begin
      maybe_main_address = home_address if prefers_home_address?
      maybe_main_address = work_address unless maybe_main_address
      maybe_main_address = addresses.first unless maybe_main_address
    end
  end
end

The begin...end creates a block of code in Ruby that can be treated as a single thing, kind of like {...} in C-style languages. That’s why ||= works just as well here as it did before.

But there is a chance for `nil` so can use like bellow

class User < ActiveRecord::Base
  def twitter_followers
    return @twitter_followers if defined? @twitter_followers
    @twitter_followers = twitter_user.followers
  end
end


class User < ActiveRecord::Base
  def main_address
    return @main_address if defined? @main_address
    @main_address = begin
      main_address = home_address if prefers_home_address?
      main_address ||= work_address
      main_address ||= addresses.first # some semi-sensible default
    end
  end
end

https://www.justinweiss.com/articles/4-simple-memoization-patterns-in-ruby-and-one-gem/