On Tue, Feb 2, 2010 at 8:09 AM, Stephen <sblackst...@gmail.com> wrote:
> There seems to be a limitation on how one can use the options hash with
> to_json. Take this example:
>
> render :json => { :results => @posts.to_json(:only => [:title] ) }
>
> You don't end up with what you want; instead of results being an array of
> posts, results becomes an escaped string. I recently put a patch on
> lighthouse that would cover this specific case but after some further
> thought, I think a more general solution is in order.
>
> Suppose to_json rather than returning a String instead returned a
> JSONString. We could then create an encoder for JSONString which does not
> re-escape itself when to_json is called on it.
>
> You would then be free to do something like the example above and it would
> all "just work". You'd also be able to pass different options to
> different AR collections being returned in the same result.
>
> Are there any other thoughts out there on this?
The problem is that to_json is really the wrong API for providing
custom JSON output.
We nearly always want to transform an object into *JSON-encodable
primitives*. Not into a JSON string.
So we split the brittle to_json API into as_json and to_json. Rather
than implement to_json to return a string, implement as_json to return
a JSON-encodable primitive. to_json converts the object using as_json
before encoding.
class Foo
# new way: return a JSON representation
def as_json
{ :foo => bar }
end
# old way: return a JSON string
def to_json(*ugly_internal_options)
{ :foo => bar }.to_json(*ugly_internal_options)
end
end
In short, this allows you to do
render :json => { :results => @posts.as_json(:only => [:title] ) }
jeremy
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