What is the content type of json file to AWS S3 with ruby? - ruby-on-rails

Question

I'd like to upload json file to S3 by ruby with paperclip. I coded as following, but it returned the following error.
undefined method `merge' for "application/json":String
Could you tell me how to set content-type of json-file?
product_definition.rb
class ProductDefinition < ActiveRecord::Base
belongs_to :product
has_attached_file :meta_data,
:storage => :s3,
:s3_credentials => "#{Rails.root}/config/s3.yml",
:url => ":s3_domain_url",
:path => "/assets/:id/:style/:basename.:extension",
:s3_host_name => "s3-ap-northeast-1.amazonaws.com"
validates_attachment :meta_data, content_type: 'application/json'
end
products_controller.rb
#product_definition = ProductDefinition.create(meta_data:sample.json)

Answer 1

If you're using a recent version of Paperclip it looks like you formatted the arguments to validates_attachment_content_type incorrectly. I think it should be:
validates_attachment :meta_data, content_type: { content_type: 'application/json' }
See the example in the Paperclip Readme: https://github.com/thoughtbot/paperclip#validations
EDIT: How I came to this conclusion is by noticing the error says it tried to call merge on the string. Merge is meant to be called on a Hash, so therefore it expects a Hash value for :content_type.

Answer 2

What you have is exactly what the current docs on github state, but it does not work:
https://github.com/thoughtbot/paperclip
Other examples use a different way of formatting matching types - so very confusing.
What does seem to work, is a syntax-change which appears to date back years, which is:
validates_attachment :meta_data, attachment_content_type: {content_type: 'application/json'}
You can also put a set of acceptable content-types in an array, such as
validates_attachment :meta_data, attachment_content_type: {content_type: ['application/json', 'application/doc']}