Ruby複製驗證

Question

擁有屬於某個類別的產品。想要在短時間內創建促銷活動（可以說是一週或兩週），但在此期間，它們只能針對每個類別進行一次促銷。

如何爲此創建自定義驗證？

product class 
    belongs_to :categories 

    name:string 
    desc:text 
    reg_price:decimal 
    category_id:integer 
    promo_active:boolean 
    promo_price:decimal 
    promo_start:datetime 
    promo_end:datetime 
end 

category class 
    has_many :products 

    name:string 
end 

更新到可能的解決方案？

class Product < ActiveRecord::Base 
    attr_accessible :name, :desc, :reg_price, :category_id, :promo_active, :promo_price, :promo_start, :promo_end 

    belongs_to :category 

    #validate :check_unique_promo 
    #Tweaked original to be more exact and 
    #Give clue if its the start or end date with the error. 
    validate :check_unique_promo_start 
    validate :check_unique_promo_end 

def check_unique_promo 
    errors.add_to_base("Only 1 promo allowed") unless Product.count(:conditions => ["promo_active = ? AND promo_end < ?", true, self.promo_start]) == 0 
end 

def check_unique_promo_start 
    errors.add_to_base("Start date overlaps with another promotion.") unless self.promo_active == false || Product.count(:conditions => ['promo_end BETWEEN ? AND ? AND category_id = ? AND promo_active = ? AND id != ?',self.promo_start, self.promo_end, self.category_id, true, self.id]) == 0 
end 

def check_unique_promo_end 
    errors.add_to_base("End date overlaps with another promotion.") unless self.promo_active == false || Product.count(:conditions => ['promo_start BETWEEN ? AND ? AND category_id = ? AND promo_active = ? AND id != ?',self.promo_start, self.promo_end, self.category_id, true, self.id]) == 0 
end 
end 

我跳過自我，如果promo_active錯誤的表現。

Answer 1

我會用validates_uniqueness_of驗證這樣：

class Product < ActiveRecord::Base 
    belongs_to :categories 
    validates_uniqueness_of :promo_active, :scope => :category_id, :allow_nil => true 

    before_save :update_promos 

    private 
    def update_promos 
    # custom code to set :promo_active to nil if the promo is 
    # not active and to something else if it is active 
    end 
end 

以2：

validate :check_unique_promo 

def check_unique_promo 
    errors.add_to_base("Only 1 promo allowed") unless Product.count(:conditions => ["active_promo = 1 AND promo_end < ?", self.promo_start]) == 0 
end