Rails：从没有模型的表中检索值(Rails: retrieve values from a table without a model)

Rails：从没有模型的表中检索值(Rails: retrieve values from a table without a model)

在rails中有没有办法从没有任何模型的表中检索值？ 我创建了一个表item_types，其中包含字段name和item_id，其中item_id是另一个表项的主键。 items表中的每个项目可以有3个或4个item_types。 在这里，我想显示具有特定item_id的项目的相应item_types。 我们只是在变量@ item.id中有一个特定项的item_id我试过形成一个sql查询，但我不知道如何在没有模型的情况下实现它。 此外，我不确定下面查询的'item_id = @ item.id'部分是否正确。

select * from item_types where item_id = @item.id

In rails is there any way to retrieve values from a table which does not have any model? I have created a table item_types with the fields name and item_id in which item_id is the primary key of another table items. Each item in items table can have 3 or 4 item_types. Here I want to display the corresponding item_types of an item with a particular item_id. We just have the item_id of a specific item in a variable @item.id I have tried forming an sql query, but I don't know how to implement it without a model. Also I am not sure whether the 'item_id = @item.id' part of the query below is correct.

select * from item_types where item_id = @item.id

最满意答案

您正在查看的是join_model ，它可以与has_and_belongs_to_many或has_many :through关系一起使用

我不知道你想要实现什么，但我强烈建议在你的独立模型中使用has_many :through association：

#app/models/type.rb Class Type < ActiveRecord::Base has_many :item_types has_many :items, through: :item_types end #app/models/item.rb Class Item < ActiveRecord::Base has_many :item_types has_many :types, through: :item_types end #app/models/item_type.rb Class Type < ActiveRecord::Base belongs_to :item belongs_to :type end

这将允许您通过其他模型调用join_model ，如下所示：

@item = Item.find(params[:id]) @item.item_types #-> calls SQL "select * from item_types where item_id = @item.id"

这是正确的Rails方法。 HABTM不使用模型; HMT确实如此。 您应该使用@Bharat Soni's评论生成模型并使用我的代码段访问它

What you're looking at is a join_model, which can either be used with a has_and_belongs_to_many, or has_many :through relationship

I don't know what you're trying to achieve, but I would highly recommend employing a has_many :through association in your independent models:

#app/models/type.rb Class Type < ActiveRecord::Base has_many :item_types has_many :items, through: :item_types end #app/models/item.rb Class Item < ActiveRecord::Base has_many :item_types has_many :types, through: :item_types end #app/models/item_type.rb Class Type < ActiveRecord::Base belongs_to :item belongs_to :type end

This will allow you to call the join_model through your other models, like this:

@item = Item.find(params[:id]) @item.item_types #-> calls SQL "select * from item_types where item_id = @item.id"

This is the correct Rails way to do this. HABTM doesn't use a model; HMT does. You should generate a model using @Bharat Soni's comment & access it with my snippet