Rails/Ruby 提取 if 阻塞到助手或守卫

Question

In my Rails app I need to implement authentication for web app, I need to use an external resource to make it work. To do so I'm using custom Devise Strategies. After a tremendous amount of work, I finally managed to implement a code that covers all scenarios - the code is working but unfortunately my eyes bleed when I see the code below:

module Devise
  module Strategies
    class AwareLogin < Authenticatable
      def authenticate!
        # some logic
        # (...)

            if login.valid_password?(password) && aware_response.success?
              success!(login)
            elsif login.valid_password?(password) && !aware_response.success?
              success!(login)
            elsif login.id.nil? && aware_response.success?
              login.set_user_tokens(aware_response)
              success!(login)
            elsif !login.valid_password?(password) && !aware_response.success?
              raise ActiveRecord::Rollback
            elsif !login.valid_password?(password) && aware_response.success?
              fail!(:aware_auth)
            end

          rescue SupervisorRollback => s
            @user_to_rollback = s.user_id
            raise ActiveRecord::Rollback
          end
        end
      end
    end
  end
end

Is there any way to replace that if block by something clearer like guard or even maybe external helper instead?

Answer 1

You can consolidate the logic a bit but given that the branches perform different actions you will still need some of the branching.

My recommended consolidation

def authenticate!
  begin
    if login.valid_password?(password) || (set_token = login.id.nil? && aware_response.success?) 
      login.set_user_tokens(aware_response) if set_token
      success!(login)
    else 
      aware_response.success? ? fail!(:aware_auth) : raise(ActiveRecord::Rollback)
    end 
  rescue SupervisorRollback => s
    @user_to_rollback = s.user_id
    raise ActiveRecord::Rollback
  end
end 

Reasoning:

• Your first 2 conditions only differ in their check of aware_response.success? ; however whether this is true or false they perform the same action so this check is not needed.
• Third branch performs 1 extra step of setting a token. Since this branch is unreachable unless .login?valid_password?(password) we have simply added an or condition to the first branch and to conditionally set the token if this condition is true
• The 4th and 5th conditions can be reduced to an else because we checked if login.valid_password?(password) is true in the first branch thus reaching this branch means it is false. Now the only difference is how we respond to aware_response.success? which I just converted to a ternary.

Note: There may be uncovered scenarios in your original example, due to the fact that there is no else . Theoretically login.id.nil? &&.aware_response?success? login.id.nil? &&.aware_response?success? is uncovered and other mutations of such; however I am unfamiliar with the possible options in this specific case. My solution will cover these additional scenarios but possibly not as intended, for example: login.id.nil? &&.aware_response?success? login.id.nil? &&.aware_response?success? could result in nil using your branching whereas it will result in raise(ActiveRecord::Rollback) under mine.