Ruby on Rails 多态模型：动态字段
假设我有基本模型类 Item
class Item
include Mongoid::Document
field :category
end
每个类别确定 item 应包含哪些字段。例如，“category1”中的项目应包含名为 text 的附加字符串字段，“category2”中的项目应包含字段 weight 和 color。所有字段都是基本类型：字符串、整数等。
这些附加值将作为文档字段存储在 mongodb 中：
> db.items.find()
{ "_id" : ObjectId("4d891f5178146536877e1e99"), "category" : "category1", "text" : "blah-blah" }
{ "_id" : ObjectId("4d891f7878146536877e1e9a"), "category" : "category2", "weight" : 20, "color" : "red" }
类别也存储在 mongodb 中。字段的配置由管理员在运行时定义。
> db.categories.find()
{ "_id" : "category1", "fields" : [ { "name" : "text", "type" : "String" } ] }
{ "_id" : "category2", "fields" : [
{
"name" : "weight",
"type" : "Integer"
},
{
"name" : "color",
"type" : "String"
}
] }
用户需要使用 html 表单来编辑项目，输入为特定项目类别定义的所有附加字段的值。
问题是
我可以采取什么方法在rails上实现这种多态性？
请询问所需的详细信息和评论。
Suppose I have base model class Item
class Item
include Mongoid::Document
field :category
end
Each category determines which fields should item contain. For example, items in "category1" should contain additional string field named text, items in "category2" should contain fields weight and color. All the fields are of basic types: strings, integers and so on.
These additional values are to be stored in mongodb as document's fields:
> db.items.find()
{ "_id" : ObjectId("4d891f5178146536877e1e99"), "category" : "category1", "text" : "blah-blah" }
{ "_id" : ObjectId("4d891f7878146536877e1e9a"), "category" : "category2", "weight" : 20, "color" : "red" }
Categories are stored in the mongodb, too. Fields' configuration is defined at runtime by an administrator.
> db.categories.find()
{ "_id" : "category1", "fields" : [ { "name" : "text", "type" : "String" } ] }
{ "_id" : "category2", "fields" : [
{
"name" : "weight",
"type" : "Integer"
},
{
"name" : "color",
"type" : "String"
}
] }
Users need to edit Items with html forms entering values for all additional fields defined for the category of particular item.
The question is
What approaches could I take to implement this polymorphism on rails?
Please ask for required details with comments.
如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱，如果其他用户或者作者回复了您的评论，将不能在第一时间通知您！
发布评论
评论（1）
只需对 Item 进行子类化，Mongoid 就会处理其余的事情，例如存储类型。
Rails 会喜欢它，但您可能想要使用 #becomes 方法，因为它会让表单生成器满意并且路径生成更容易：
https://github.com/romanbsd/mongoid/commit/9c2fbf4b7b1bc0f602da4b059323565ab1df3cd6
Just subclass the Item, and Mongoid will take care of rest, e.g. storing type.
Rails will like it, but you'll probably want to use #becomes method, as it will make form builder happy and path generation easier:
https://github.com/romanbsd/mongoid/commit/9c2fbf4b7b1bc0f602da4b059323565ab1df3cd6