Rails3：控制生成的JSON（使用datamapper ORM的to_json）

问题描述

在我的Rails 3应用中，我想要这样的JSON：
{count：10，
图片：[
{id：1}，
...]}
我尝试过

  render（：json => {：count => 10，：pictures => @ pictures.to_json（：only =>：id）}）
  

但在这种情况下，我的图片逃脱

  ... pictures： [{\ id\：2653299}，.. .. 
  

在旧的merb应用程序中，我的控制器中包含以下简单行：

  display（{：count => @count，：pictures => @pictures}）
  

因为我使用 datamapper 作为我的ORM和 dm-serializer 我不确定在哪里影响生成的json。

解决方案

您的代码应该是：

  render（：json => {：count => 10，：pictures => @pictures}）
  

不调用：to_json exp

但是，如果没有此提交，它将在dm-1.0中轰炸： http://github.com/datamapper/dm-serializer/commit/64464a03b6d8485fbced0a5d7> b
$ b

我想它将很快发布，但与此同时它很容易打补丁。

编辑

我忽略了您要在集合中使用：only => [：id]的事实。看起来：as_json出于某种原因尚未在Collections上实现。您可以通过几种方式解决此问题。您的示例可能看起来像这样：

  render（：json => {：count => 10，：pictures => ; @ pictures.map {| p | p.as_json（：only => [：id]）}}）
  

这会将您的图片收藏转换为ID的哈希。然后render将正确地执行它，并且您应该得到想要的结果。 （希望如此）

From my Rails 3 app i want a JSON like this: {count:10, pictures:[ {id:1}, ... ] }I tried

render( :json => { :count => 10, :pictures => @pictures.to_json(:only=>:id) } )

but in this case, my pictures get escaped

..."pictures":"[{\"id\":2653299}, ....

In my old merb app I had the following simple line in my controller:

    display( { :count=>@count, :pictures => @pictures } )

Because I am using datamapper as my ORM and dm-serializer I am not sure where to influence the generated json.

解决方案

Your code should be:

render( :json => {:count => 10, :pictures => @pictures })

without calling :to_json explicitly on @pictures (the same as it was in your merb app).

However, this will bomb in dm-1.0 without this commit: http://github.com/datamapper/dm-serializer/commit/64464a03b6d8485fbced0a5d7150be90b6dcaf2a

I imagine it will be released soon, but in the meantime it's simple to patch.

edit

I overlooked the fact that you want to use :only => [:id] on your collection. It looks like :as_json has not been implemented on Collections for whatever reason. You can get around this in several ways. Your example might look like this:

render( :json => {:count => 10, :pictures => @pictures.map {|p| p.as_json(:only => [:id])}} )

That will turn your Picture collection into a hash of IDs. render will then do its thang properly and you should get your desired results. (hopefully)

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