在Ruby / Rails中使用if / then为当前状态创建范围

Question

I'm trying to figure out how to create a scope for 'late' jobs.

A 'late' job will be one where the state is :in_progress where the :due date is older than today.

(I'm not using any state gems and have Postgres as the database).

This is what I have going so far. I'm fairly new to if then statements and have only created basic scopes to this point. Any thoughts on how to go about this in my model?

# states

  STATES = %w[bids in_progress complete canceled]
  delegate :bids?, :in_progress?, :complete?, :canceled?, to: :current_state

  def current_state
    (events.last.try(:state) || STATES.first).inquiry
  end

# scope

  def self.late
    if @current_state_jobs == :in_progress?
      where('due < ?', Time.now) 
    else
      nil 
    end
  end

Can I use the first current_state scope in the late scope? I'm not sure

Answer 1

I'm not sure I fully understand your setup, but I can certainly help steer you in the right direction.

I don't believe your delegate statement will work because as far as I know it needs to set the :on option to an object of some sort and not a method. In your case, what I think you need to delegate to is state.inquiry . There's probably a way to do that, but I'm afraid I don't know how.

Here is a quick discussion on delegates that seemed pretty helpful to me:

http://www.simonecarletti.com/blog/2009/12/inside-ruby-on-rails-delegate/

With that in mind, these delegate methods are still instance methods, and a scope needs class methods.

I'm not sure what @current_state_jobs is supposed to be, but that's an instance variable and you're in a class function so I don't think it works. I think what you're really looking for is simply where(state: "in_progress") .

Next you want to do a query on the date which is actually kind of tricky. If you're not careful, Time.now sort of gets binded when the module is first loaded. To prevent that, you need to use a lambda function to ensure the time is based on when the function is called.

Also, you said in the description that you want the method to include anything that is "older than today", but what your query is doing is anything "older than right now".

To sum it all up I think you need something like this:

scope :late, lambda { where("state=? and due < ?", "in_progress", Date.today) }

If it were me, I'd probably break it into two different scopes like in_progress and overdue then have :late just be in_progress.overdue , but if you're not going to use either of those other two scopes then it's unnecessary.

I hope that helps.