如何在Rails的计算中使用枚举数据库值（数字）？

Question

In my app I have a model that has 2 different enum parameters associated with it. I want to use these parameters in a calculation (essentially taking the database numerical value of each and adding them together) and return a result. Ideally I want to iterate through these model objects, sum their enum values and use the result to provide a score to the parent object.

Here is my model - it's for a SWOT analysis:

class Swot < ActiveRecord::Base
belongs_to :sales_opportunity, inverse_of: :swots
validates :swot_details, presence: true
validates :sales_opportunity_id, presence: true
enum swot_type: [:strength, :weakness, :opportunity, :threat]
enum swot_importance: [:minimal, :marginal, :noteworthy, :significant, :critical]
before_save :update_opportunity_score

def update_opportunity_score
    sales_opportunity.update_swot_score
    sales_opportunity.save
end
end

I'm trying to write the code for the update_swot_score function but I'm totally lost as to how to achieve it. What I need is the ability to extract all swots that are "strength" and sum the swot_importance values (1 for "minimal, 2 for "marginal"... 5 for "critical"), then do the same with "weakness", "opportunity" and "threat" before using the summed score in a calculation.

I've been playing around with the code below, but now I'm just totally lost as to what I'm doing. Any help would be appreciated.

def update_swot_score
    strength = SalesOpportunity.swots.where("swot_type <> ?", Swot.swot_types[:strength]).each do |strong|
        SalesOpportunity.swots.swot_importances[strong.swot_importance]
end
end

Answer 1

Rails enums provide a helpful array of options and integer values. In rails console, run Swot.swot_importances and see. So, you can just lookup from that array:

class Swot < ActiveRecord::Base
  belongs_to :sales_opportunity, inverse_of: :swots
  validates :swot_details, presence: true
  validates :sales_opportunity_id, presence: true
  enum swot_type: { strength: 1, weakness: 2, opportunity: 3, threat: 4 }
  enum swot_importance: { minimal: 1, marginal: 2, noteworthy: 3,
                          significant: 4, critical: 5 }
  before_save :update_opportunity_score

  def update_opportunity_score
    sales_opportunity = swot_score
  end

  def swot_score
    Swot.swot_types[swot_type] + Swot.swot_importances[swot_importance]
  end
end

Note that there's no need to specify self. in a model. Also, you always want to use save! unless you're checking return values since save can fail. But saving in a before callback is redundant. Also, you should specify the integer values of your enums explicitly since you're relying on them for business logic.