Question

Lets say Bookshelf has_many :books. I can dump a bookshelf to json, including it’s associated books like this:

@bookshelf.to_json :include => [:books]

But I want a simple ruby hash instead. I’ve tried #attributes but that doesn’t appear to take any arguments. And i’ve tried #to_hash but that method doesn’t on ActiveRecord::Base.

I know I could do this:

JSON.parse @bookshelf.to_json(:include => [:books])

But that feels like a huge and ugly performance waste. I’m sure it’s compiled to a hash internally before its JSON-ified, so I dont want to have to do an extra round of encode/decode for no reason.

Answer 1

In Rails 2.3 you can use as_json:

The as_json call is very helpful for this situation. It can take attributes and it returns a hash, though the keys are a little odd when you start including nested objects. Specifically, the keys for the current object are all strings, and the key for the handle of the nested object is a symbol.

So, for your example, your call could look something like:

hash = @bookshelf.as_json(:include => {:author => {}, :books => {:include => :pages}})

And access to the hash object would look something like:

hash["bookshelf_color"] #=> "White"
hash[:author]["name"] #=> "John Smith"
hash[:books][:pages]["format"] #=> "8.5 inches x 5.5 inches"

In Rails 3.0 you can use serializable_hash:

The v2.3 as_json functionality moved to the serializable_hash method. It works the same as the above (looking at the source code you can tell the v2.3 as_json method was moved to the v3.0 serializable_hash method).