Rails Serialized JSON -> no implicit conversion of Hash into String

Question

Having collected some JSON from a file using the Curb gem, I assign a portion of it to an instance variable:

self.json_stuff = {"title" => json["title"], "description" => json["description"], "image" => json["image"]}.to_json

This then gets stored in the database as JSON:

serialize :json_stuff, JSON
...
self.save

Later on I check for the presence of said json_stuff:

return self.json_stuff.present?

And get the following error:

TypeError - no implicit conversion of Hash into String:
  json (1.8.3) lib/json/common.rb:155:in `initialize'
  json (1.8.3) lib/json/common.rb:155:in `new'
  json (1.8.3) lib/json/common.rb:155:in `parse'

I've stepped through the code and I know that the collection of the JSON from the file is done without issue.

Could you give use more information please, first of all what does p self.json_stuffprints ? Furthermore, I think you try to encode your object two times, the first one with .to_json which give you a string, and then when you save id with the serialize action, could you try to remove .to_json from your first line ? — ex0ns
– ex0ns, Commented Aug 24, 2015 at 15:05
when I try to inspect the variable in the rails console I get the same error : no implicit conversion of Hash into String... I'll look in to the suggestion of it being encoded twice... Thanks for the pointer... — TheRealJimShady
– TheRealJimShady, Commented Aug 24, 2015 at 15:09
...tried removing to_json but still getting the same error... When I get the json from the file, I parse it using JSON.parse, is this correct? — TheRealJimShady
– TheRealJimShady, Commented Aug 24, 2015 at 15:17
I didn't mean have I used JSON.parse correctly, I mean was I right to use JSON.parse at all? — TheRealJimShady
– TheRealJimShady, Commented Aug 24, 2015 at 15:20

Roope Hakulinen · Accepted Answer · 2015-08-24 15:05:37Z

1

As far as I know, the present? method is for Strings to check if they are not empty. If you just want to return boolean based on the existence of json_stuff you should check if it is nil for example with

return self.json_stuff.nil?

The type of self.json_stuff is Hash instead of String.

answered Aug 24, 2015 at 15:05

Roope Hakulinen

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