Rails - 从查找表访问时间戳

Question

我试图从查找表中创建的时间戳获取值。假设我有Ingredients和Recipes，还有一个名为ingredients_recipes的表，其中有ingredient_id，recipe_id，然后是时间戳。

我该如何访问这些时间戳？基本上，我需要知道什么时候将某种成分添加到配方中。

谢谢！

Answer 1

所以你现在有这样的事情？

class ingredient << ActiveRecord::Base 
    has_and_belongs_to_many :recipes 
    ..... 
end 

class recipe << ActiveRecord::Base 
    has_and_belongs_to_many :ingredients 
    .... 
end 

而你想获得他们添加的日期。轨道的方式是通过使用连接模型。 （见http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html）和许多。特别是这条线Choosing which way to build a many-to-many relationship is not always simple. If you need to work with the relationship model as its own entity, use has_many :through. Use has_and_belongs_to_many when working with legacy schemas or when you never work directly with the relationship itself.

所以，如果你在哪里建立一个连接模型，你会得到像下面的东西。

class ingredient << ActiveRecord::Base 
    has_many :mixtures 
    has_many :recipes , :through=> :mixtures 
    ..... 
end 

class recipe << ActiveRecord::Base 
    has_many :mixtures 
    has_many :ingredients, :through=> :mixtures 
    .... 
end 

class mixture << ActiveRecord::Base 
    belongs_to :recipe 
    belongs_to :ingredient 
    ... 
end 

这种方式可以将属性添加到混合物表，所以你可以发现，当他们在那里补充说，谁补充他们等等