Find existing session

I have this method in my rails app:

def find_or_create_session(fbid)
    @sessions = Session.all
    if @sessions.find_by facebook_id: fbid
      @session = @sessions.find_by facebook_id: fbid
      if ((Time.now - @session.last_exchange).fdiv(60)).to_i > 5
        @session = Session.create(facebook_id: fbid, context: {})
      end
    else
       @session = Session.create(facebook_id: fbid, context: {})
    end
    @session
end

It retrieves all the Sessions, and tries to find one with a given facebook_id. If there is one, it checks if it's a recent one (last_exchange was less than 5 minutes ago). If it's not, it creates a new one.

If it can't find a session for this facebook_id, it will create one.

This is pretty easy, but it seems to be a lot of if/else for such a straightforward thing.

Some notes:

• @session: A method called find_or_create_session should not change the state of instance variables.

• @sessions.find_by facebook_id: fbid is written twice. Use variables to avoid repetition. Also, the consensus in the Ruby community is to always write parens (except for DSL-like code).

• Time.now - @session.last_exchange: You can perform that check in the SQL query.

• Your method is basically doing find_or_create_session = existing_session || new_session, let the code mimic it.

I'd write:

def find_or_create_session(fbid, max_age: 5.minutes)
  Session.find_by(["facebook_id = ? AND last_exchange >= ?", fbid, max_age.ago]) ||
    Session.create(facebook_id: fbid, context: {})
end

StackExchange Code Review Q#126744, answer score: 4