Question

In ruby:

class Obj
  attr_accessor :price
end

my_ruby_obj = Obj.new

puts my_ruby_obj.to_json

"\"#<Obj:0x1c9b018>\""

Server sends my_ruby_obj.to_json to browser (sinatra, with content_type :json) in response to a jquery ajax request (with $.get), which correctly defines a return type of json, and launches a callback function(data) which does:

console.log(data);

which returns:

#<Obj:0x1c9b018>

Now how do I access “data.price” attribute in javascript/jquery as I would normally do on a ruby object to access its attribute? (“my_ruby_obj.price”)

I tried with console.log(data.price);

> Undefined

I feel I am missing a big piece here.. and I guess it has to do with how json works with objects..

Any help ?
If possible, I’m looking for a correct way to do it with jquery.

Thanks

edit:
trying to understand what is going on, I tried this in the callback:

newdata = $.parseJSON(data);

but debug console halts on it showing:

> uncaught exception: Invalid JSON: #<Obj:0x1c9b018>

I did call .to_json on the ruby object, so why it says so? …

[[new_edit:]]

Seems like ruby json serialization for objects from custom classes is not working as I supposed:

Quoting from here: https://stackoverflow.com/a/4464721/988591

It will be a bit more difficult for objects from your own classes. For
the following class, to_json will produce something like
"\"#<A:0xb76e5728>\"". This probably isn’t desirable. To effectively
serialise your object as JSON, you should create your own to_json
method.

and examples are following…
But.. wow… isn’t there an easier way ?

Answer 1

Ok I found exactly what I was looking for! An automated quick solution, which also comes with other side benefits (more speed!).

The standard json gem only works for some classes (Array, Hash,..) and can’t translate a custom class/object you have created to JSON. It doesn’t know how to organize data, unless you write yourself a custom .to_json method for your class, which is what I was tring to avoid..

So in the end I found a gem called Oj: Optimized Json (gem install oj)

Quoting the authors:

Optimized JSON (Oj), as the name implies was written to provide speed
optimized JSON handling. It was designed as a faster alternative to
Yajl and other the common Ruby JSON parsers. So far is has achieved
that at about 2 time faster than Yajl for parsing and 3 or more times
faster writing JSON.

Oj has several dump or serialization modes which control how Objects are converted to JSON. These modes are set with the :mode option in
either the default options or as one of the options to the dump()
method.

:object mode will dump any Object as a JSON Object with keys that
match the Ruby Object’s variable names without the ‘@’ character. This
is the highest performance mode.

I used it like so:

json = Oj.dump(guy, mode: :object) but in my case it worked without mode: :object as well.

now console.log(data); shows:

({'^o':"Human", x:38, y:58, name:"Jack", bday:{'^t':1352083824.5625}, age:50})

Now that the serialization is working good, I can finally do:

console.log(data.age); // —> 50

Serialization is faster too.

..It has been a long ride though 😉

A big Thank You goes to the library author: http://twitter.com/#!/peterohler