Ruby-on-rails Rails 对象关系和 JSON 渲染
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Rails Object Relationships and JSON Rendering
提问by M. Ryan
Disclaimer, I know very little about Rails. I'll try to be succinct. Given the following model relations in Rails:
免责声明，我对 Rails 知之甚少。我会尽量简洁。鉴于 Rails 中的以下模型关系：
class ModelA < ActiveRecord::Base
belongs_to :ModelB
...
class ModelB < ActiveRecord::Base
has_many :ModelA
When calling the show action of the ModelA controller the returned JSON should show all ObjectAs that are children of the ObjectB of which the ObjectA in question is a child of.
当调用 ModelA 控制器的 show 操作时，返回的 JSON 应该显示所有 ObjectA，它们是 ObjectB 的子级，而有问题的 ObjectA 是其子级。
So if I have an ObjectB that contains ObjectA's of ID 1, 2 and 3 and then access: /modela/1.json
因此，如果我有一个包含 ID 1、2 和 3 的 ObjectA 的 ObjectB，然后访问：/modela/1.json
I should see:
我应该看到：
{
"modelb": {
"id": "1",
"modela": [insert the ModelA JSON for ID's 1, 2 and 3]
}
}
回答by Rob Cameron
By default you'll only get the JSON that represents modelbin your example above. But, you can tell Rails to include the other related objects as well:
默认情况下，您只会获得modelb上面示例中表示的 JSON 。但是，您也可以告诉 Rails 包含其他相关对象：
def export
@export_data = ModelA.find(params[:id])
respond_to do |format|
format.html
format.json { render :json => @export_data.to_json(:include => :modelb) }
end
end
You can even tell it to exclude certain fields if you don't want to see them in the export:
如果您不想在导出中看到它们，您甚至可以告诉它排除某些字段：
render :json => @export_data.to_json(:include => { :modelb => { :except => [:created_at, updated_at]}})
Or, include only certain fields:
或者，仅包括某些字段：
render :json => @export_data.to_json(:include => { :modelb => { :only => :name }})
And you can nest those as deeply as you need (let's say that ModelB also has_many ModelC):
您可以根据需要将它们嵌套得尽可能深（假设 ModelB 也有_many ModelC）：
render :json => @export_data.to_json(:include => { :modelb => { :include => :modelc }})
If you want to include multiple child model associations, you can do the following:
如果要包含多个子模型关联，可以执行以下操作：
render :json => @export_data.to_json(include: [:modelA, :modelB, :modelN...])
回答by Chau H?ng L?nh
If you want a more flexible approach to rendering json, you can consider using the gem jbuilder: https://github.com/rails/jbuilder
如果你想要更灵活的渲染json的方式，可以考虑使用gem jbuilder：https: //github.com/rails/jbuilder
It allows you to render custom attributes, instance variables, associations, reuse json partials in a convenient way.
它允许您以方便的方式呈现自定义属性、实例变量、关联、重用 json 部分。
