Wraps the parameters hash into a nested hash. This will allow clients to submit POST requests without having to specify any root elements.

它有助于省略包装哪些参数哈希. Action Controller overview guide给出了这个破败：

Rails collects all of the parameters sent along with the request in the params hash,whether they are sent as part of the query string or the post body. […] The query_parameters hash contains parameters that were sent as part of the query string while the request_parameters hash contains parameters sent as part of the post body. The path_parameters hash contains parameters that were recognized by the routing as being part of the path leading to this particular controller and action.

当您使用RESTful资源和路由时,会发生这种乐趣.假设你有一个模型A has_many Bs;因此B具有外键a_id.

你使用空载荷POST / as / 1 / bs(因为B没有其他字段).假设a_id是attr_accessible,可以假设a_id将包装在b对象中.相反,你会看到：

Processing by BsController#create as HTML
  Parameters: {"b"=>{},"a_id" => "1"}

没有这样的运气.事实证明,ParamsWrapper uses request_parameters而不是params,因此在POST有效载荷中不包括a_id意味着它不会被包裹.这是非常令人困惑的,因为你仍然看到它包含在params中,由于URI globbing,并且想知道为什么它被排除在所有东西之外.

有没有什么好的理由在这里使用request_parameters而不是params？

我可以理解,从“REST哲学”的角度来看,如果我们假设有效载荷包含整个对象,它就更纯粹了,但这实际上意味着URI中的a_id被完全忽略,这似乎很可惜.

tl; dr：ParamsWrapper使用request_parameters作为参数源,因此跳过了URI-globbed变量.这是一个Rails错误吗？纯REST倡导者可能会说不,但实用主义暗示是.