Man. I was really having fun coding up JSON responses in one of my Rails apps. Until, that is, I wanted to do something custom.
Now, you might ask, “Why would you want to do something custom?”
To which I would reply, “Sigh. Because I’m just that way.”
Get on with it
Ok, I’ve got this ActiveRecord model called Fact. Fact has attributes :key and :value along with the other normal columns (i.e. :id, :created_at, etc.).
I want to use Fact in one of my views and I export it to JSON. I only care about the :key and :value and the obvious solution is to:
fact = Fact.create(:key => 'foo', :value => 'bar')
fact.to_json(:only => [:key, :value])
Which returns something like:
{"key": "foo", "value": "bar"}
Ok … fine. I can do something with that, but Fact is really an extension of some other model, which can have many Facts. And I want to reference these facts by their name in a JavaScript object. I don’t want to search through the objects looking for a matching key. I want a JavaScript Object that looks something like:
{"foo": "bar"}
You might say, “Get over it!”
I would say, “No. This is what I want.”
I also figured it would be easy to modify Fact to return what I want. What I figured was that since I could call to_json on an ActiveRecord, the implementation of to_json would actually recursively work its way through the hierarchy of attributes and associations and call to_json on each of them. Thinking this was the case, I went and wrote my own to_json on Fact.
“What happened?”, you ask.
“Bupkiss”, I say.
“What do you mean?”, you persistently ask.
“What’s with all the questions!”
The reason why nothing happens is because to_json hands responsibility over to the ActiveRecord::Serialization::Serializer class (ASS). ASS in turn builds up its own Hash of keys and values that it grabs from the ActiveRecord in question.
This is NOT what I would expect. Hence, my annoyance. In fact, I find it a little silly and a little broken. If this is what I expected, I would instead pass an instance of Fact to a JSON encoder and Fact would in fact know nothing of JSON. As it stands, Fact knows about JSON and JSON knows about Fact (by knowing about ActiveRecord).
Whatchu goan do?
I don’t know yet. I’ll repost when I figure it out. I just wanted to post my annoyance. I am very, very annoyed.
