英文:
How to preload in gorm many to many with the condition in join table
问题
这是翻译好的内容：
我又来了...
现在对我来说有一个大问题，但我很难思考它
现在我可以在gorm中预加载。但是当在多对多表中使用预加载和连接表时...我遇到了一些我不知道的问题
我有3个表
type Product struct{
Categories []Category `gorm:"many2many:Product_Category"`
}
type Category struct{}
type Product_Category struct {}
类似这样的。我现在可以使用Preload("Categories").Find(&products)
但问题在于如何通过类别筛选产品？
也就是说，我需要在预加载类别时在连接表Product_Category中添加条件吗？有没有解决方案？
此外，我想知道如何将带有类别的产品添加/更新到Product和Product_Category这两个表中？
英文:
It's me again...
Now the big issues for me but I hard to think about it
Now I can preload in gorm. But when using preload for many to many table with the join table... I have some issues that I dont know
I have 3 table
type Product struct{
Categories []Category `gorm:"many2many:Product_Category"`
}
type Category struct{}
type Product_Category struct {}
some kind like that. I now can using Preload("Categories").Find(&products)
But the problem here is how can I filter the product with category?
Mean I need to add the condition in the join table Product_Category when preload the category? Are there any solutions?
And beside that, I wonder how to add/update the product with categories into 2 table Product and Product_Category?
答案1
得分: 3
这段代码的意思是：
- 创建一个多对多的关系，其中一个模型的外键是ID，引用为"product_id"，另一个模型类似。
- 然后，你只需要简单地预加载Categories。
英文:
type Product struct{
Product
Categories []Category `gorm:"many2many:product_category;foreignKey:ID;joinForeignKey:ProductID;References:ID;joinReferences:CategoryID"`
}
type Category struct{}
type Product_Category struct {}
This says
- Create a many 2 many relationship with 1 foreign key being id of one model with reference as "product_id" and similar for other.
- then all you need to do is simply preload Categories
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