Rails: JSON.pretty_generate(obj) in the controller does not produce pretty output

Question

I need a pretty output of the JSON for an activerecord object in the rails controller. Based on the answer to this question by jpatokal, I tried the following:

respond_to do |format|
  format.json { render :json => JSON.pretty_generate(record) }
end

where

record

is an activerecord object. It does not produce a prettified output. However, when I try outputting a hash using the same code, viz,

respond_to do |format|
  format.json { render :json => JSON.pretty_generate({"abc" => "1", "def" => "2"}) }
end

it does produce a prettified output (so pretty_generate is working, and so is my browser).

How do I use pretty_generate to produce a pretty output of an activerecord object?

presuming you explicity added `gem install json` to your Gemfile? — blotto, Feb 12 '14 at 00:18
I didn't. However, it is there: $ gem list | grep "json" json (1.7.5) multi_json (1.3.6) — ppd, Feb 12 '14 at 00:23
my suggestion is to try in rails console next, and exclude the format.json code. basically see if `> JSON.pretty_generate(record)` exhibits the \n chars. — blotto, Feb 12 '14 at 00:42
Thanks for that tip. In the console, record.to_json produces the json for the object. However, `> JSON.pretty_generate(record)` gives the following error: `NoMethodError: undefined method 'key?' for #`. It appears that record cannot be serialized correctly? — ppd, Feb 12 '14 at 00:59
sounds like the instance is a complex object, not easily serlialized. try some other json parser like `gem yajl-ruby` — blotto, Feb 12 '14 at 01:06
before that, maybe even try `JSON.pretty_generate(record.as_json)` and/or `JSON.pretty_generate(record.to_json)` in console — blotto, Feb 12 '14 at 01:08

score 6 · Accepted Answer · edited Mar 10 '15 at 15:57

To get pretty output of JSON from an active record object you have to first request the object as JSON.

record.as_json

The above code will do this for you, the short way to render out pretty JSON from the controller is:

render json: JSON.pretty_generate(record.as_json)

This also solves the "only generation of JSON objects or arrays allowed" error you can get trying to convert AR objects to pretty_generate JSON.

EDIT: I forgot to mention this can all be done in rails 4.1.8 and above (possibly even earlier) using the standard json and multi-json gems packaged with rails project.

Rails: JSON.pretty_generate(obj) in the controller does not produce pretty output

1 Answers1