防止用户模型在Rails中多次加载

Question

I have a situation where the user model is used multiple times in the same query in different places. For example: I want to iterate through all the groups the users is a member of, and get a unique list of all his/her friends that are also members of these groups.

Right now the user model gets reloaded every time, which results in: 1) Performance hit 2) Ideally I would use an instance variable to hold the unique list of friends, but I cannot do it since the user model gets reloaded.

It would make a lot of sense for the user model to be global for the duration of the request - any idea how I could achieve that?

Answer 1

Assuming that with "the user model" you actually means the current user instance (the User model is used to reference the model defined bu the class User) you normally use a memoization technique.

For instance, given you have a current_user method in your controller, you can do

def current_user
  return @current if defined?(@current)
  # In the following line load the current user. It's the first time
  # this method is requested. Further calls will return the cached instance.
  @current = ...
end

Answer 2

You can set a user like this:

def current_user
  @current_user ||= User.find(1)
end